Chapter 13: The Chemical Mortar in the Pacific
The employment of chemical mortar units in the Pacific differed considerably from that in the Mediterranean and European theaters. With the halt of the general Japanese advance at Guadalcanal, Allied forces faced the prospect of subjugating or bypassing the many island groups that lay between them and Japan. Because some of the islands were not very large certain of the campaigns were to be fought by small task forces, with a single mortar platoon attached to a regimental combat team. The islands also dictated that there would be a great many amphibious operations in which the 4.2-inch mortar, mounted on landing craft, was gradually to assume an important role. In many cases the advancing Allies were confronted by thick jungle growth which hindered the use of artillery and enhanced the value of the more mobile 4.2-inch mortar. This terrain, consisting of dense vegetation broken only by an occasional path, created problems of observation and transportation even for chemical mortar units. The climate of the Pacific added to the difficulties of mortar operations; the heavy rain, intense heat, and high humidity of the tropics made it difficult to insure effective employment of the mortar and proper maintenance of the weapon and its ammunition.
South Pacific Area
The initial combat employment of chemical mortar units in the war against Japan took place in September 1943 during the fight for New Georgia in the South Pacific Area.1 It must be re-emphasized that the CWS did not receive authorization for the high explosive mission for 4.2-inch mortars until 19 March 1943, nearly seven months
after U.S. forces first landed on Guadalcanal. For the Allies the Guadalcanal operation was the beginning of the road back. More immediately it had the mission of blunting the Japanese advance and protecting the vital lifeline between Australia and the United States.2 With Guadalcanal secured, American forces looked northwest up the Solomon Island chain that led to New Britain and the important Japanese base at Rabaul. The Russell Islands fell first; then came the New Georgia campaign with its focal point at Munda, the site of an enemy airfield. The attack on the island of New Georgia began on 2 July 1943.
The 82nd Mortar Battalion was the first and only battalion in the South Pacific Area. Under command of Lt. Col. William H. Shimonek, the unit arrived at New Caledonia on 19 July 1943, too late to see action in the Munda operation. After a few weeks of training on Guadalcanal, elements of the 82nd Battalion entered the mopping-up operation on Arundel and Kolombangara Islands in the New Georgia group. Assigned to XIV Corps and attached to the 43rd Infantry Division, a platoon of B Company landed on what was to be known as Mortar Island in the Stima Lagoon area. This platoon fired its first combat rounds on the morning of 10 September when, under control of the division artillery, it delivered harassing and interdictory fire against the enemy, some of it on enemy barges operating between Kolombangara and Sagekarasa Islands.3
Meanwhile, in close support of the 27th Infantry, 25th Division, another platoon of the mortar battalion, moved up to Bamboe Peninsula on Arundel Island. The men used jeeps, hand carry, and a variety of boats to negotiate the difficult terrain. Once in position the mortars fired at enemy barges and troops. Despite the extreme range mortar fire destroyed three barges, causing the loss of enemy troops and supplies. From 25 September to 4 October the mortars placed cross-channel fire on the airfield on Kolombangara Island and on enemy shipping in the narrow waters between the islands.
These initial mortar operations were accompanied by certain problems, notably those involving transportation and supply. Major
McKaig, chemical officer of the 25th Division, improvised methods to provide the transportation and manpower necessary to resupply mortar units. Shipped from Guadalcanal to New Georgia by LST and from New Georgia to the northern end of Arundel Island by LCT (landing craft, tank) , the ammunition was then transferred by LCMs to a battalion dump at the west end of Sagekarasa Island. From there engineer ponton boats took the ammunition across a lagoon to the mortar platoon’s unloading points at the other end of the island.4
Although infantry commanders were unfamiliar with the capabilities and limitations of the mortar, most troops recognized the satisfactory performance of both the mortar crews and the weapon. And it was the opinion of a prisoner of war that the Japanese feared mortar barrages more than those of the artillery. One criticism by supported units was the great number of tree bursts which occurred in the heavy jungle canopy and which resulted from a lack of a delayed action fuze.5
The 82nd Battalion next saw action on Bougainville, the largest of the Solomon group. Operations on this island began on the first day of November 1943 when the 3rd Marine Division spearheaded the assault landings of the I Marine Amphibious Corps, with the 37th Infantry Division landing a week later. The XIV Army Corps, composed of the 37th and Americal Divisions, took over from the marines on 15 December. The corps commander, Maj. Gen. Oscar W. Griswold, indicated his desire to employ chemical mortar units in place of corps artillery in situations where the use of the latter was impracticable.
During and after the all-out enemy counterattacks on the American perimeter around Empress Augusta Bay in March 1944, infantry divisions attached mortar platoons to regiments or battalions. Control of the weapon varied. In the Americal Division mortar units operated directly under the supported infantry organizations, while in the 37th Division the mortarmen received firing instructions through the fire direction center of the artillery battalion to which they were attached. Both methods were satisfactory, but direct contact with the supported infantry seemed preferable since it allowed greater responsiveness during changing situations and provided closer liaison with responsible
commanders.6 Heavy barrage missions were normally coordinated with corps and division artillery.
The jungle foliage on Bougainville was so thick that forward observers, compelled to employ sound-sensing methods of observation, were often located only 30 yards from the enemy and directed fire to within 20 yards of their own observation post and of the front lines. During the height of one enemy attack, the mortars placed smoke shell directly in front of enemy forward elements while troops of the 182nd Infantry, only 30 yards away, withdrew without casualties. This was one of the few uses of WP on Bougainville, since the smoke further reduced the jungle’s limited visibility.
Infantry commanders soon recognized that the mortars could engage, with a weight of shell comparable to that of 105-mm artillery, many targets which could not be reached by the 105s and 155s. To insure adequate fire coverage of the entire 13-mile perimeter, thirty mortar positions were established which were linked together by more than 150 miles of communications wire. The necessity for this unusual number of gun positions was well demonstrated during one 4-day period in March by simultaneous requests from the 129th, 145th, and 182nd Infantry for supporting fire from the platoons of Company A.
Daily battalion expenditure of mortar shell on Bougainville during March was extremely heavy; during the last three weeks of the month Company A alone expended 20,250 rounds in defense of a hill held by elements of the Americal Division. In an 11 March mission Companies A and D massed fire with 75-mm. and 105-mm. howitzers and with 60-mm. and 8 1-mm. mortars in a preparation which helped repel an enemy attack. Twelve days later Companies C and D joined with seven artillery battalions and two cannon companies in the heaviest general supporting fire laid down in the South Pacific fighting.
Field artillery officers were impressed by the amount of effective fire produced by a chemical mortar company as compared to that of an artillery unit. Maj. John D. Tolman, who commanded the 82nd Chemical Mortar Battalion from 26 April until the close of the Luzon Campaign, disclosed that infantry commanders felt they could not “properly accomplish [their] mission [without] 4.2-inch mortar
support.”7 The 37th Division considered the 4.2-inch mortar “a powerful and devastating supplement to the division’s artillery and mortar fires,” and commanders of the Americal Division, while recommending reduction of the minimum range to increase the weapon’s flexibility, commented on the effectiveness of the chemical mortar in perimeter defense and for fire on reverse slopes.8 Captured Japanese documents revealed the enemy’s fear of the weapon; enemy artillery was instructed to concentrate on American mortars.9
Infantry and chemical battalion commanders on Bougainville indicated that they were unfamiliar with each other’s organization, tactics, and procedures and recognized the need for joint unit training. This reciprocal unfamiliarity continued to be a problem whenever a mortar unit was committed for its first engagement or a division had a chemical mortar unit attached to it for the first time.10
Beginning at Bougainville securing mortar crews against enemy infiltrations became a serious problem, particularly during night missions. Because of the absence of infantry perimeter guards and the frequency of enemy infiltrations, the battalion provided for day and night shifts both at the gun positions and at forward observation posts. Single and double apron fences surrounded emplacements. Automatic rifles and grenades were the chief means of repulsing Japanese attempts to overrun mortar positions.
The relatively static nature of the battle for the perimeter around Empress Augusta Bay eased the problem of maintenance. On the coral rock soil of Arundel, Company B had broken five base plates, bent five or six tie rods, and cracked several barrel cups and base plate spades. On Bougainville, despite the heavy and continuous fire, the softer ground and the fact that time was available to construct adequate emplacements resulted in a minimum of damage to mortar parts. The torrential rains, high humidity, and intense heat of South Pacific islands created serious problems both in the maintenance of mortar shell and its
components. During the heaviest downpours, firing ceased because excessive water in the barrel resulted in “poop-outs.” The extreme heat melted the filling of white phosphorus shells, creating a lateral void for those rounds stored in a horizontal position. These rounds tumbled badly when fired. A lack of adequate waterproofing combined with dampness caused the malfunction of cartridges and propellants and corrosion of fuzes while shells were in storage. In an attempt to minimize these difficulties on Bougainville mortarmen placed their ammunition dump, featured by sheltered racks and a double-decked roof, as far inland as possible. Even then ammunition had to be checked and rechecked, particularly the fuzes. Although heat, rain, and dampness continued to be a problem throughout operations in the South and Southwest Pacific, the situation improved in late 1944 with the introduction of metallic containers for propellants and cartridges.
At least one difficulty with mortar shells was not brought on by the weather. This was the occasional absence of the steel balls which prevented the premature arming of the fuze. Despite close inspection of mortar ammunition short rounds and premature bursts resulted in several casualties to both mortarmen and infantry.11
Southwest Pacific Area
New Guinea
Early in 1943 the Chemical Warfare Service,12 the War Department, and Southwest Pacific Area headquarters considered the possibility of shipping chemical mortar units to the Southwest Pacific.13 The area’s demand for these units grew more insistent after a weapons demonstration held in October 1943. At the demonstration General Krueger, Commanding General, Sixth Army, told Maj. Gen. William H. Gill, Commanding General, 32nd Infantry Division, that the 4.2-inch chemical mortar was the weapon needed to clean the enemy out of tenaciously
held positions.14 Several other high-ranking commanders who had participated in the Buna campaign in Papua, where mortar battalions had not been available, echoed this opinion. They suggested that a chemical mortar battalion be made a part of army troops for attachment to corps and divisions.15
In April 1944 General MacArthur launched a new offensive along the northern coast of New Guinea in a series of operations which, in collaboration with Admiral Nimitz’ drive through the Central Pacific, would place American forces in a position to retake the Philippine Islands. On 22 April MacArthur’s initial objectives, Hollandia and Aitape, were attacked by I Corps operating as RECKLESS Task Force.16
The elements of RECKLESS Task Force had chemical mortar support for the Hollandia operation, but this support came from a rather odd source. Because of a shortage of mortar units in the zone of interior the War Department in February 1944 authorized the SWPA to convert a tank destroyer battalion to a chemical mortar battalion at the earliest practicable date. Almost immediately the theater reorganized the 641st Tank Destroyer Battalion which, after a brief period of training, participated in the Hollandia operation, under command of Lt. Col. Alexander Batlin. But redesignation waited until June 1944, producing the anomalous situation of a so-called tank destroyer unit firing 4.2-inch chemical mortars.17
The mortars played an extremely minor role at Hollandia, the entire four companies firing less than 350 rounds during about one week in the line. At the request of a regimental commander one company dragged a single mortar and 120 shells on carts for twelve miles along a narrow, muddy mountain trail, across a 2,000-foot ridge, through swamps, and over three rivers—only to arrive too late to support the fight for Hollandia Airdrome. It was fortunate that expenditures were low because ammunition was limited. On the night of 23 April enemy planes bombed the beachhead dumps at Humboldt Bay destroying 6,550
rounds of 4.2-inch mortar shell, or about 78 percent of the available supply.18
Subsequent New Guinea operations utilized but one mortar company at a time. Company B of the 98th, commanded by 1st Lt. Vernon E. Woebbeking and attached to the 191st Field Artillery Group, successively supported the 163rd, 158th, and 10th Infantry Regiments during the Wakde Islands—Maffin Bay fighting which took place in May 1944. During the assault phase of this operation, the LCMs carrying the 4.2-inch shell grounded over fifty yards from the beach and the mortar crews had to carry their cargo through chest-deep water.19 During the cross-channel firing on the Wakde group the chemical mortars massed fires with the 81-mm. mortars and with the artillery from the mainland. When attached to artillery units the mortar platoons were divided into 2-gun sections with weapons placed approximately 1,000 yards apart. Chemical officers and Sixth Army headquarters vigorously criticized this practice because it prevented the units from massing their fires and giving close support to the infantry. They insisted that platoons be employed as units under direct infantry control.20 Later, mortar units were assigned to the infantry and remained so attached for the rest of the operation.
In June 1944 HURRICANE Task Force, principally composed of two of the three regiments of the 41st Division, assaulted the island of Biak, located west of Wakde off New Guinea’s northern coast.21 The Allied forces wanted the island, as they had Wakde, as a site for airfields for bombing operations against the enemy. Company D, 98th Battalion, commanded by Capt. Jalmar Gertulla, supported the attacking forces with missions for perimeter defense, beachhead extension, and harassment. On one occasion the 2nd Platoon covered the withdrawal by water of a tank-led infantry battalion and then, after destroying their mortars and ammunition, withdrew itself. Early in June observers of the mortar platoon directed fire from landing craft on cave mouths
invisible to both air and ground observers. Unfortunately, when the 1st Platoon fired 180 rounds of high explosive at cave mouths for an antitank company on 7 June, 10 out of 12 rounds with T-89 delay fuzes were duds, while other rounds with point-detonating fuzes exploded as tree bursts above the caves.
What might be considered classic examples of combined all-mortar preparations took place on 16 and 27 June. Chemical mortar barrages preceded advances of the 186th Infantry near the village of Mokmer on Biak; this fire was then lifted and was followed successively by the 81-mm and the 60-mm mortars. On both dates, the infantry advanced against minor resistance to objectives which, before these preparations, had been vigorously defended.22
With the Wakde experience in mind the 20th Infantry inquired whether a chemical mortar company could be assigned to the 6th Infantry Division. After Biak, supported battalions in the 162nd and 186th Infantry Regiments stated that because of its greater range and blast effect on area targets, the 4.2-inch mortar filled the gap between the 81-mm. mortar and artillery. Because of the higher angle of fire, the infantry preferred the 4.2-inch mortar to 75-mm. and 105-mm. howitzers for firing on sharply defiladed and densely wooded terrain. In open terrain the mortar was equal in effectiveness, if not range, to the 105-mm. howitzer. On the other hand, two battalion commanders considered the 4.2-inch mortar less accurate than the 81-mm. weapon and complained of the slow displacement of the former over rough terrain during a fast-moving advance.23
The 98th Battalion encountered some of the same tribulations on New Guinea that had marked the fighting in the South Pacific Area. These included the unfamiliarity of infantry commanders with the capabilities and limitations of the weapon, the inadequate training of mortar personnel in infantry tactics and procedures, the excessive length of time firing personnel remained in the line without relief, and the deleterious effects of dampness on mortar shell components and their containers. The disadvantages of attaching mortar units to artillery
organizations, realized in the South Pacific, were emphasized in the Southwest Pacific.24
Beginning with the fighting on New Guinea, one of the most persistent of the bottlenecks facing mortar units was the lack of adequate motor transportation. Several times the units were unable to keep up with supported infantry in fast-moving actions. At Hollandia and on Wakde ship-to-shore movement suffered seriously from a shortage of amphibious vehicles. In the former operation, one company failed to land in time to carry out its mission in support of an infantry regiment. The value of adequate motorized equipment from ship to shore and from the shore inland was again illustrated on Biak where assignment to the company of 4 Dukws and 3 additional 2½-ton 6 x 6 trucks insured prompt and speedy landing of men, weapons, and shell; facilitated leapfrogging of platoons during movement of the company along beach areas; and resulted in satisfactory ammunition resupply. Colonel Arthur, Chemical Officer, 41st Division, as well as the G-3 of I Corps, felt that mortar units should be committed with complete organic transportation and urged that the companies be provided with either 2 LVTs (landing vehicles, tracked) or 4 Dukws for amphibious movement.25
Leyte
In September 1944, with the northwest coast of New Guinea in the hands of General MacArthur and with the Marianas Islands secured by Admiral Nimitz, the Joint Chiefs of Staff, deciding to skip three planned intermediate objectives, set their sights directly on the island of Leyte in the Philippines.26 In a move that speeded up the Pacific time
table by exactly two months, they directed MacArthur and Nimitz to assault Leyte on 20 October.27
At the time of the Leyte invasion Sixth Army included X Corps and XXIV Corps. The latter had been at Pearl Harbor preparing for the assault on the island of Yap when the change of plans eliminated that particular operation. Thereupon Admiral Nimitz turned over the XXIV Corps to General MacArthur. Major elements of XXIV Corps were the 77th and 96th Divisions, having among their supporting units the 88th Chemical Mortar Battalion (less companies C and D) , and the 7th Division, supported by the 91st Chemical Company. The latter, one of two separate mortar companies to see action in World War II, had been stationed for some years at Schofield Barracks on Hawaii.28
Chemical mortar units already with Sixth Army were the 98th and the 85th Battalions. The former, having participated in the Wakde and Biak fighting, had entered a period of rest and rehabilitation. The 85th Chemical Mortar Battalion, a recent arrival from the United States, supported X Corps in the Leyte operation, specifically the 1st Cavalry and 24th Infantry Divisions.
Commanded by Lt. Col. Kenneth K. MacDonald, the 85th Battalion landed on the beaches of Leyte with the early waves of the 20 October assault. The battalion was divided into two groups, corresponding with its attachments—the headquarters detachment and Companies A and B with the 1st Cavalry and Companies C and D with the 24th Division. Company C ran into immediate difficulty. Coming in with the fourth wave the two landing craft carrying the 3rd Platoon received direct hits from enemy fire. One man was killed and 10 others were wounded. But in general, enemy resistance was light, and this circumstance, combined with a lack of transportation, limited initial activity for the companies of the 85th Battalion. Companies C and D had landed without organic vehicles and were to operate under that handicap for the entire campaign.
During the second and third weeks of November, Company C supported the 21st Infantry, 24th Division, in the extremely bitter fighting for Breakneck Ridge, southwest of the town of Pinamopoan located on the northern coast of Leyte. The Japanese defended this position
with a tenacity that gave the hill formation its nickname. For a time the rugged terrain limited artillery support, a situation which enhanced the value of the CWS weapon. The mortar platoons fired nearly 2,800 rounds of ammunition during the period 7-15 November, including missions against troop concentrations, entrenchments, pillboxes, mortars, machine guns, and light artillery.
On 14 November the 32nd Division relieved the 24th Division and, as so often was the case, Company C of the 85th Battalion remained in the line in support of a new infantry regiment, this time the 128th. Within four days an incident occurred which marred good relations between the supporting and supported units. On the morning of 18 November the mortars of Company C, along with other supporting weapons, fired about 375 rounds against an enemy strongpoint. Despite the testimony of the mortar forward observer, the division chemical officer, and the regimental commander himself, Company C was charged with a short round burst that killed one infantryman of the 128th and wounded seven others. The X Corps commander, Maj. Gen. Franklin C. Sibert, ordered the relief of the mortar company, an action which took place six days later with the arrival of Company B. Unfortunately, this incident destroyed the confidence of the infantry in the chemical mortar; for quite a while thereafter the division employed the 4.2-inch mortar only for road interdiction.29
Company B, 88th Chemical Mortar Battalion, commanded by Capt. Henry A. Kitselman, came ashore with elements of 96th Division (XXIV Corps) over the beaches near Dulag.30 During the first two weeks of combat the platoons of the company operated separately in support of infantry battalions in attacks in the vicinity of the landing beaches, against enemy positions on Labiranan Head, Labir, and Catmon Hill, and inland near the villages of Tabontabon and Dagami. Initially, the swamp and poor transportation prevented the mortars from getting inland and thereafter transportation proved to be a major problem. During this period, which coincided with the rainy season, the vehicles of the mortar company became mired, while advancing infantrymen
were calling for fire now beyond mortar range. The mortars did complete some missions. On 22 October one of the mortar platoons repulsed an attack of a Japanese patrol killing 52 of the enemy and itself suffering 2 killed and 6 wounded. Later, on 27 and 28 October, the mortars silenced enemy 75-mm. mortars in defilade on Catmon Hill, burned four sniper-infested pillboxes, and screened the withdrawal of an infantry company pinned down on Catmon Hill.
From 5 to 20 November Company B, firing as a unit, supported the 382nd Infantry and then, until 28 November, the 381st, which was slowly advancing through the swamps, rice paddies, and hilly terrain west of Dagami. Mortarmen, with the aid of Filipinos, carried their weapons and ammunition by hand, or placed them on the backs of plodding carabao. The intense rain continued to hamper all ground operations. It caused base plates to sink into the soft mud and resulted in mortar breakage and the consequent suspension of firing.
Company A, 88th Chemical Mortar Battalion, landed with the 77th Division early in December 1944 and remained with that unit for two months. The 91st Chemical Mortar Company supported the 7th Division throughout the Leyte Campaign. Although placed under control of division artillery, each of its three platoons supported one of the three regiments of the division. During this 41-day commitment, two platoons used artillery forward observers and one used its own. In the drive on Ormoc the division artillery assumed control of the mortar company. Although no missions took place under this arrangement the platoon fired for registration every evening. In mid-December two of the platoons reverted to regimental attachment, a step which in the opinion of the company commander, Capt. Eugene F. Them, resulted in a far better utilization of the unit.31
The performance of the 4.2-inch mortars on Leyte was not an unqualified success. Infantrymen frequently complained that the mortar units could not keep pace with them in rapid advances over rough terrain, a situation resulting as much from the rainy season in which the operation took place as from the lack of complete organic transportation among the mortar units. This lack stemmed directly from the infantry’s unfamiliarity with the needs of mortar units—only one of the six divisions which saw action had had previous chemical mortar support. As a result, most of them failed to allot sufficient shipping
space for the mortar units and most organic vehicles were not taken aboard.32 Only when the supported divisions and regiments assigned additional transportation to the mortar companies did the latter recover their mobility.33 At the conclusion of the Leyte operation chemical officers not only recommended the use of Dukws for mortar units in assault landings, but also the employment of tracked vehicles in swampy terrain.34
Luzon
Turning his attention from Leyte, where he left the newly activated Eighth Army, to Luzon, General MacArthur directed General Krueger to seize a beachhead on Lingayen Gulf, drive southward and free Manila, and, eventually, liberate the entire island.35 The decision to take Luzon had come only after prolonged debate at the highest level of strategic planning. S-day for the operation was 9 January 1945.36
Sixth Army operations on Luzon had the support of three mortar battalions.37 The 98th Chemical Mortar Battalion supported I Corps on the left of Sixth Army’s beachhead and the 82nd fired for the divisions of XIV Corps on the right. The 85th Battalion was released from the Eighth Army later in January and attached to XIV Corps. These three mortar battalions provided continuous close support throughout the fighting on Luzon. As on Leyte, the corps normally reattached mortar companies to divisions which, in turn, assigned platoons to assault regiments.
Initially, XIV Corps faced but token resistance as it headed down the central plain of Luzon toward Manila. Enemy opposition increased in the last week of January, particularly in the Zambales Mountains on
the right flank of the corps. After a week marked by effective mortar fire against personnel, weapons, tanks, and supply dumps, three companies of the 82nd turned southward to join in the struggle for Manila. The fourth, Company B, remained behind in the hills west of Fort Stotsenburg, successively supporting elements of the 40th, 43rd, and 38th Divisions from 28 January to 18 March. Mortar operations in support of a 40th Division attack on Snake Hill North were featured by some unusual action on the part of forward observers. On 7 February, after enemy fire wounded a platoon forward observer, Cpl. Edward A. Yehle of the mortar observation party successfully directed chemical mortar and artillery fire against enemy opposition in front of a battalion of the 160th Infantry. Next morning another mortarman, Pvt. Herbert H. League, took charge in a similar situation, simultaneously directing 4.2-inch mortar, 81-mm. mortar, and artillery fire in action which resulted in the destruction of at least one enemy machine gun and which served as a screen for the evacuation of friendly casualties. Later, League directed similar fire which proved instrumental in the death of 40 Japanese and in repulsing an enemy attack.
Meanwhile, the main body of the 82nd supported the 37th Division as XIV Corps pushed down Route 5 toward Manila. The approach to the city was uneventful in comparison to the resistance encountered once the American forces entered Manila. Fire missions for the mortars picked up immediately. The weapon screened regimental crossings of the Pasig River, which bisects the city, and fired support, incendiary, and neutralization missions, mostly in conjunction with infantry mortars and the artillery. After witnessing the chemical mortars in action before the High Commissioner’s residence, the Assistant Chief of Staff, G-3, 37th Division, declared that “direct support infantry weapons, particularly 4.2-inch mortars, falling close to our own lines, were found to neutralize the enemy where penetration took place.”
The 85th Battalion was triangularized just prior to landing near San Fabian in the Lingayen Gulf on 28 January with the 1st Cavalry Division.38 By early February, its mortars were in Manila supporting cavalrymen from emplacements on city pavements, vacant lots, lawns, golf courses, even tennis courts. From 2 2 to 25 February elements of Company B fought as infantry in defense of a regimental perimeter within the city.
Certain supported commanders, particularly in the 7th Cavalry Regiment, refused to use chemical mortars for close support missions, claiming that the old M2 sight was inaccurate.39 But it was with this sight that elements of the 8 5th massed fire, along with 81 -mm. mortars, in the final assault on the Agriculture Building and brought fire to within 200 feet of the mortar observation post. After the cavalry took its objective, a regimental operations officer called the chemical mortar fire “the most accurate fire support we’ve ever had.” Battalion casualties, the highest for a 30-day period of any chemical mortar battalion on Luzon, totaled 7 men killed and 13 wounded.
During the last part of February and before resistance had ended in Manila, XIV Corps gave the 1st Cavalry Division (less one brigade) and the 6th Infantry Division, until recently a part of I Corps, the mission of clearing the Manila watershed and attacking Japanese forces in the Sierra Madre Mountains about ten miles east of the city. These enemy troops, comprising the major enemy concentration in central Luzon, had not taken part in the Manila fighting but had withdrawn to the east with the approach of the American troops. Ensconced in the so-called Shimbu Line, Japanese forces put up fanatic resistance in the rugged and rocky foothills of the Sierra Madres.
The 82nd and 85th Chemical Mortar Battalions fired in support of these operations. Company A, 85th Battalion, saw a good deal of action with the 7th and 8th Cavalry regiments west of Antipolo. Early in March a squadron commander refused to have one of the mortar platoons engage a target because it was within 500 yards of his troops. Instead, he gave the mission to his 81-mm. mortars, despite the fact that these weapons had a greater dispersion than did the 4.2s. This show of hesitancy regarding mortar support by the 85th Battalion was not the first to come from supported troops. A succession of battalion commanders—there were three incumbents during the first six weeks of 1945—provides another clue to the fact that not all was right with the unit. As of 16 March the firing companies of the 85th reverted to battalion control and underwent an intensive 2-week training period under the new commander, Maj. Maurice G. Green, recently operations officer of the 82nd Chemical Mortar Battalion.
The 82d Chemical Mortar Battalion supported the Shimbu
operations from 25 February until 30 April. In mid-March the XIV Corps relinquished control of this fighting to XI Corps, and the 8 2nd utilized this transfer of command to reorganize under the latest table of organization. Battalion support in the vicinity of Mount Mataba, one of the bastions of the Shimbu Line, resulted in some of the heaviest 4.2-inch mortar fire in the Pacific war. During the 2-week period between 23 March and 5 April the 82nd fired nearly 190 missions with an expenditure of over 22,000 rounds. On 6 April two platoons of Company B and one from Company C, in support of an attack by the 63rd Infantry, laid a 6,000-yard smoke screen southeast of Mount Mataba and maintained it for eight hours. The smoke masked the advance of the infantry from enemy observation posts on Mount Mataba and a lesser hill which was an immediate objective of the attack. The mortars maintained this screen by firing a total of 16 rounds a minute the first hour and to rounds a minute thereafter. Unfortunately, a shortage of ammunition brought a halt to the screen before the troops reached their objective. Three hours later ammunition requested from XI Corps four days earlier arrived at the mortar positions.40
On 21 April Company B (less the 3rd Platoon) , while in support of the 145th Infantry, participated in one of the heaviest preparations fired on Luzon. In order to cover an infantry advance on the slopes of Mount Pacawagan, another of the keys to the Shimbu positions, the mortar company fired 2,525 rounds of white phosphorus to set up a 7-hour screen, supplemented by two B-25 aircraft laying a 8,000-yard FS screen. Six days later the crest of Pacawagan fell to troops of the 145th Infantry after a combined weapons preparation and with the aid of a chemical mortar screen.
That the reputation of smoke increased on Luzon is suggested by the following entry in a 6th Infantry Division operational report: “The outstanding use for chemical warfare weapons in the Shimbu Line battle was the use of screening smokes. ...”41 One of the mortar battalions called attention to the high ratio of white phosphorus used on Luzon,42 indicative of quite a departure from previous Pacific practice.
Infantry commanders had long been reluctant to request WP fire. Smoke as a means of concealment was often superfluous in the jungle fighting during the early years of the war, and casualties were produced by high explosives. As a consequence, white phosphorus ammunition remained unused while stockpiles of high explosives were bled white.
Actually, white phosphorus ammunition was a versatile munition. In addition to its ability to produce screens and inflict casualties, it served as an incendiary agent. A fourth characteristic, really an extension of its antipersonnel capability, was the tremendous psychological effect it had on the enemy. The main reason for its unpopularity was that infantry commanders were unfamiliar with its many attributes, especially the casualty and incendiary effects.43
Several factors contributed to the increased use of smoke shell on Luzon. One of these was the limited supply of high explosive shell which served to call attention to the white phosphorus munition. In February 1945, for example, Col. Richard R. Danek, Chemical Officer, XIV Corps, declared that the supply of chemical mortar ammunition had “reached a critical stage.”44 Several months later Maj. David D. Hulsey, 6th Division chemical officer, stated that during one period in April chemical mortar operations in his sector were “practically nil” because of the “unavailability of 4.2-inch mortar ammunition from XI Corps.”45 Causes for the shortage included limited transportation and deterioration of shell through improper storage, but, more basically, the critical nature of the supply of 4.2-inch mortar ammunition on Luzon resulted from the fact that half of the shells received from the United States were on the list of ammunitions frozen by the War Department because of the possibility of defective fuzes.46
Other reasons for the increased use of WP involved matters of terrain and education. In the Philippines, American forces for the first time in the Pacific encountered a battle area of rather extended dimensions and one that featured mountain and hill masses from which the enemy had excellent observation. The Sierra Madres east of Manila and the series
of mountains confronting I Corps in its drive to the northeast were typical of the Luzon terrain. A 6th Division report gave examples of the use of screening smokes: “... to deny the enemy observation during infantry attacks, to cover the construction of supply roads, and to screen carrying parties and evacuation of wounded.”47 As for the matter of education, supported commanders, once they had seen the results of WP as an antipersonnel and incendiary agent, were much less loath to call for WP rounds in support of their operations.
Perhaps the best barometer of the reputation of white phosphorus was the official HE–WP ratio for mortar ammunition which fluctuated back and forth between 80–20 and 60–40, in favor of high explosives. In August 1945 General MacArthur’s headquarters established the ratio at 60 HE–40 WP, based upon the experience of the major combat commands of the theater.48
While XIV Corps landed against light resistance and faced only token enemy forces until the Fort Stotsenburg fighting, I Corps had a tough time almost from the start. The enemy had established strong defenses on I Corps left flank, made more formidable by the rugged mass of hills and mountains. The fact that the Japanese headquarters lay to the rear of these defenses tended to make enemy resistance all the more tenacious. The divisions of I Corps faced not one but a series of difficult missions. Elements were to drive southeast across central Luzon, cover the left flank of the southward advance of XIV Corps, and advance north and northeast in the direction of the towns of Damortis and Rosario and an important road junction just beyond.
An immediate I Corps objective was the enemy position in the Cabaruan Hills, fifteen miles inland from the Lingayen beaches in the sector of the 6th Division. On 22 January Company A, 98th Chemical Mortar Battalion, operating as a unit for the first time on Luzon, supported the 2nd Battalion, 20th Infantry, in what was expected to be the culminating effort against Japanese resistance in the Cabaruan Hills.49 The mortar platoons went into positions about 200 yards from one another in defiladed terrain. Each unit maintained its own observation post on one of the highest hills in the area. These OPs
were located about 350 yards in front of the mortars and overlooked the enemy positions 600 yards to the front. Wire connected the observation posts with the mortars, although once the platoons moved forward they would have to rely exclusively upon radio communication. At this stage in the fighting the forward observers of all three platoons fired at targets selected by the infantry battalion commander. Ammunition resupply was the province of the regimental supply officer who delivered the shells directly to the platoon positions. When the mortar units displaced forward the regimental supply trucks kept pace.
After laying down a heavy barrage on an area of ten artillery squares, Company A placed white phosphorus on the corners of the enemy position to mark it for aerial bombardment. After the air strike the mortars blanketed the enemy area with WP as the rifle companies of the 2nd Battalion, 20th Infantry, moved forward. Companies E and F advanced along opposite sides of a ridge that led into the right flank of the Japanese positions. Company G, located initially in front of the objective, used the smoke to move through a ravine and into the left flank of the enemy-held hill mass. The 1st and 2nd Platoons of the mortar company displaced forward in rear of the cannon company; the 3rd remained ready to fire on any target of opportunity. The three mortar forward observers as well as the mortar company commander, Capt. G. B. Doolittle, accompanied Company G. During the advance radios served as the only means of communication.
Company G experienced initial success in its flanking maneuver but was suddenly hit on three sides by Japanese fire. At the same time the enemy pinned down Companies E and F. This unexpected opposition came from two sources, from the enemy that survived the pre-attack bombardments and from those who had slipped into positions under the very smoke that concealed the American advance.
Losing all of its officers, Company G began to scatter without regard for dead, wounded, and equipment. Captain Doolittle of the mortar company managed to halt the withdrawal. He contacted the infantry battalion command post with his radio, the only means of communication left on the hill, and received orders to take charge. The support infantry platoon maneuvered to the left of the enemy’s position, relieving pressure on the front. Doolittle called for fire from his three mortar platoons, which by this time had all withdrawn to their original firing positions. White phosphorus mortar rounds not only blinded the
Japanese positions but set fire to brush and grass in which they had taken cover. As enemy opposition ceased, Captain Doolittle organized parties to evacuate the wounded and then led the force in an orderly withdrawal back to the positions from which the attack began. Several days later Cabaruan Hills fell to another infantry battalion.50
During the fighting with I Corps the mortars of the 98th Battalion won a fair reputation for their ability to cope with enemy armor. Chemical mortarmen received credit for destroying at least 25 tanks, some of them dug in, and shared credit with the smaller mortars for knocking out 15 or 20 more. On 31 January, for example, after withdrawing from the edge of the town of Munoz with elements of the 20th Infantry, a mortar platoon forward observer directed fire on two enemy tanks. A direct hit knocked out one of the vehicles and subsequent mortar fire disabled a second. The mortar platoon observer crept up to this tank, jumped upon it, and hurled a grenade inside. As the tank burst into flames, the observer escaped unharmed. Four days later two Japanese tanks raced along a road directly toward a chemical mortar observation post, firing as they came. The observer directed his mortars at the first tank, setting it afire less than fifty yards from his position. The other tank turned and fled, only to be bracketed by mortar rounds. Stalled and with broken tracks, the enemy tank was set aflame by a final mortar round.51
Infantry commanders expressed satisfaction with the support given by the 98th. The 6th Division stated its preference for 4.2-inch mortar support against emplaced tanks and field pieces. After the fall of Lupao, a town vigorously defended by the Japanese, the commander of the 35th Infantry declared “the battle would have lasted days longer if the 4.2’s had not been available.”52
During mid-February 1945 I Corps began what proved to be a 4-month drive to the north to rout the enemy from the tenacious
positions of his mountain fastness.53 In this slow, gruelling campaign the 33rd Division advanced toward the port of San Fernando and toward Baguio, summer capital of the Philippines. The 32nd Division crept relentlessly along the tortuous Villa Verde Trail toward the heavily fortified Santa Fe–Imugan area, while the 25th Division moved north along Highways from San Jose to Digdig and eventually Santa Fe.
During the second week of February the companies of the 98th Battalion received assignments which were to last almost until the close of the Luzon operation: Company A was attached to the 32nd Division, Company B to the 33rd, and Company C remained with the 25th. On 21 April Company C, 8 5th Chemical Mortar Battalion, joined the forces of I Corps, supporting the spectacular drive made by the 37th Division from Santa Fe to Aparri on the northern coast of Luzon.
The 98th Battalion had to contend not only with the enemy but with the terrain and weather. The mountainous region in which the enemy held commanding positions, many of them prepared in advance, gave every advantage to the defenders. These positions, often in defilade, provided ideal targets for the accurate, high angle fire of the 4.2-inch mortars. Forward observation by ground parties, the normal procedure, was hazardous and difficult because of the superiority of Japanese observation posts. Sometimes the mortar platoons overcame this disadvantage by using artillery observers in liaison planes to conduct registration and to fire for effect.54 During March and early April the rain and muddy ground curtailed mortar shell expenditures by bogging down ammunition resupply and by compelling the constant re-emplacement of the base plates which sank out of sight after one or two rounds.
Nonetheless the weapon proved effective. Company C fired 19,000 rounds (the two other companies fired about the same number) and received credit for sealing about thirty-five caves and killing more than 250 Japanese caught in the open. The unit marked eight targets for air strike with a precision that brought praise both from Fifth Air Force and infantry commanders.
In fighting along the Villa Verde Trail, Company A fired several missions to repel enemy counterattacks, most of them during hours of darkness. Mortarmen at one time manned infantry battalion defense
positions, at the same time maintaining uninterrupted fire support of the front-line companies. Smoke shell was used for screening and casualty effect as well as for burning off occasional grassy slopes, capable of concealing the enemy, which lay in the path of the advancing infantry.
In situations like those found on Luzon, where the weapons companies of the mortar battalions were placed under the operational control of the supported divisions, battalion headquarters played an inconspicuous but important role. In the case of the 98th, for example, the headquarters and headquarters company established a permanent camp in the town of Carmen where the unit could support its weapons companies equally well. Here was the battalion rest area, and here were the battalion personnel, including weapons company clerks, an arrangement which permitted the battalion commander maximum utilization of his administrative personnel. Headquarters controlled the companies by radio and by liaison officers. The Signal Corps Radio 284 served as the basis for this communications network, proving satisfactory at times at distances twice its normal range of thirty miles.55 Liaison officers made daily visits to each of the weapons companies, contacting as many platoons as time and the situation allowed. During the course of these visits the liaison officers assisted with administrative problems, brought forward maintenance parts and certain supplies from the battalion stock, and exchanged information about the situation as it affected operations. Battalion maintained both a motor pool and radio maintenance facilities which repaired company equipment. Repairs of 8 5th Battalion equipment involving third and fourth echelon maintenance were turned over to ordnance maintenance organizations because of the lack of appropriate CWS units. Ideally, a chemical service platoon attached to division took care of the maintenance of ammunition at division dumps.
The mortar company commander set up his command post in the vicinity of the division command post or occasionally with the regiment in reserve. The mortar platoons fired for the assault battalion in each of the three regiments. Displacement forward, in ¼-ton trucks and
trailers, came upon orders of the infantry battalion commander. As in the action described at Cabaruan Hills, the mortar platoons maintained communications with the supported infantry during displacement by SCR-300 radios. Mortar platoons of the 98th Battalion maintained 35 rounds for each gun, while a 2½-ton truck loaded with 300 rounds stood by at the company command post ready to be sent forward whenever the need arose. Location of the firing positions of the mortar platoons varied from unit to unit. In the 98th Battalion, Company A’s platoons usually were established within the infantry battalion perimeter, most likely with the support infantry company. Company C, on the other hand, often set up its mortars within the infantry battalion CP perimeter.
One of the difficulties faced by the chemical mortar units on Luzon was an almost constant shortage of manpower. The 98th Chemical Mortar Battalion operated for the six months of the campaign under-strength by 5 officers and 130 enlisted men. The 82nd Battalion, while possessing a surplus of enlisted men until mid-March, was below strength from that date until the end of the campaign. The 85th Battalion experienced similar troubles.56 The lack of men was aggravated by a most inadequate number of mortar companies for the simultaneous support of 4 divisions in I Corps, 4 in XIV Corps, and 3 in XI Corps.
Reciprocal familiarity between chemical mortar and combat infantry personnel continued to be less than perfect. It was often a two-edged situation; infantry officers were unacquainted with 4.2-inch mortar potentialities, and chemical personnel, from division chemical officers to those of the mortar company, were unfamiliar with the combat techniques of the infantry. All chance had passed of attaining the ideal solution—joint training for chemical and infantry personnel, or at least familiarization lectures and demonstrations, before attachment in actual combat.57
Central Pacific Area
The Central Pacific Area lacked adequate mortar battalion support throughout the entire war.58 Despite the efforts of Colonel Unmacht, theater chemical officer, the only mortar unit available prior to May 1944 was the 91st Chemical Company (Motorized) which had been stationed in Hawaii under various designations since 1920. This unit was used in field tests, demonstrations, and joint training exercises, including amphibious assaults with several infantry divisions.
The over-all shortage of chemical mortar battalions and the higher priority of other theaters prevented shipment of these units to the Central Pacific Area until the arrival early in May 1944 of the 88th Chemical Mortar Battalion. Four months later the theater activated the 189th Chemical Mortar Company (Separate) . The only other mortar units in CENPAC were the 71st and 72nd Chemical Mortar Battalions which did not reach Hawaii until mid-1945, too late to see action before the war ended.59
The first chemical mortar action in the Central Pacific took place during the fighting on Kwajalein in the Marshall Islands when the 91st Company commanded by Capt. Joseph E. Atchison fired in support of the 7th Division. During five days in early February 1944 the unit, hampered by an ammunition shortage and severed communications lines, expended about 500 rounds while losing 1 man killed and 14 wounded.60 The next mortar unit to see action was Company C, 88th Chemical Mortar Battalion, which landed on Saipan in the Marianas with the 27th Infantry Division. Company A of the 88th played a minor role in nearby Guam. In mid-September 1944 Company D of the same battalion fired for the 81st Infantry Division on Angaur and Peleliu in the Palau group. Unlike Companies A and C, rushed to the Marianas within a month after arriving in the theater, Company D received an adequate period of orientation in Hawaii. Offsetting the advantage of thorough and extensive training was a shortage of enlisted men and motor transport. The virtual certainty that mortars and
ammunition would often have to be man-hauled led to the decision to divide the company into two 5-gun platoons.
Company D landed in the ninth wave on Red Beach, Angaur Island, on 17 September and supported the 322nd Infantry in the Solome Lake and Ramanantelo Hill areas. Attached to division artillery, the platoons fired under the direction of artillery air observers. Captured Japanese documents referred to the 4.2-inch as “that high caliber mortar,” while supported infantry commanders reported that the weapon caused heavy enemy casualties.
Company D’s 1st Platoon moved to Peleliu on 16 October, followed in a week by the 2nd Platoon and company headquarters. Attached to the 321st Infantry and later the 323rd Infantry Regiments, Company D fired normal night missions of harassment and defense as well as fourteen barrages which ignited napalm from fire bombs dropped by planes among the innumerable enemy caves and trenches.
The final campaign in the Central Pacific—operations in the Ryukyus group—saw the participation of the entire 88th Battalion as well as the 91st Company.61 In order to gain a limited fleet anchorage and seaplane base before the invasion, the 77th Division, with Company A attached, made an unopposed landing on Kerama Retto. The assault on the main objective, Okinawa, took place on I April 1945. Companies B and C of the 88th, attached to the 96th Division, landed about H plus I in the ninth and eleventh waves, respectively, in the vicinity of Chatan. Company B, commanded by Capt. Edward L. Lockman, Jr., supported the 383rd Infantry moving south along the west coast to the strong enemy defenses on Kakazu Ridge. Company C, under the command of Capt. Rutherford H. Spessard, Jr., supported the 382nd Infantry in its advance south to Nishibaru Ridge. The 91st Company, Captain Them commanding, went in on the eighth wave with the 7th Division across Purple and Orange Beaches opposite Kadena Airfield and supported the division advance to the east coast and down to the eastern approaches of the Shuri Line. At first, chemical mortar support was not available for the 1st and 6th Marine Divisions.62
Chemical mortars on Okinawa, although effective, were used almost entirely for little outside of normal missions fired according to standard methods. The only exceptions occurred when the 91st Company fired
a few times under direction of a Navy liaison observer, and when Sound Locator Teams Nos. 3 and 5 were attached to Companies C and D. From 12 April to 8 May these teams directed some firing at point targets but the extreme ranges of these targets limited the use of the mortars. During the first week, at least five Japanese night attacks, supported by tanks and artillery and directed against the 96th Division’s perimeter, were repulsed with the help of combined 4.2-inch mortar-artillery fire. In even lighter firing in support of the 7th Division, the mortars laid down small preparations by day and fired to repel Japanese infiltration raids at night. From the second week in April until mid-June, the pattern of chemical mortar support included preparations preceding infantry advance, followed, in many cases, by screens to cover U.S. troops engaged either in consolidating their positions or withdrawing with their casualties under murderous Japanese artillery, mortar, and machine gun fire. The 4.2-inch mortars than engaged in counterbattery and neutralization missions during the remaining daylight hours, followed by night harassing and interdictory fire.
On 21 April a mortarman from the 91st Chemical Mortar Company played a prominent role in repulsing a Japanese attack on the Skyline Ridge positions of the 7th Division. Here is a graphic account of this action:
When, east of the road cut, a man in the stalled third platoon, Company E, was killed, Sgt. Theodore R. MacDonnell, a 91st Chemical Mortar Company observer, was impelled to drastic action. MacDonnell had frequently joined men on the line and shown qualities of a determined infantryman. Now, infuriated, he gathered up a handful of grenades and ran in the face of the machine-gun fire along the slope to a point underneath the spot where he believed the enemy gun to be located, and then started up the 20-foot embankment. When he looked over the crest he failed to spot the gun, but he did see three enemy soldiers and grenaded them. He made two trips to the bottom of the embankment for fresh supplies of grenades, but it was not until his third trip to the crest that he located the machine gun. MacDonnell then slid back to the bottom, grabbed a BAR, and mounted the embankment with it, only to have the weapon jam after the first shot. He skidded to the bottom, seized a carbine, and went back up for the fifth time. On reaching the crest, he stood up and fired point-blank into the machine-gun position, killing the gunner and two covering riflemen. MacDonnell then hurled the machine gun down the slope behind him. A mortar that he found in the position was also sent crashing down the hillside. Sergeant MacDonnell was later awarded the Distinguished Service Cross for his heroism on this occasion.63
In an average period of seventy days in the line, each mortar company on Okinawa fired approximately 25,000 rounds, a fourth of which was WP shell. Even this rather limited amount of smoke shell appeared excessive to Tenth Army field artillery officers, particularly as in their opinion an “indiscriminate use of smoke, not only by artillery, but by other supporting weapons, obscured both air and ground observation.” Most of the Army and Marine divisions participating in the operation commented favorably on the performance of the chemical mortars and their crews. Both the 96th Infantry Division and the 1st Marine Division recommended that a chemical mortar company, and preferably a battalion, be attached regularly to a division. The Tenth Army suggested that each division receive the support of a mortar battalion and that the battalion be employed as a unit only and not fragmented by a series of attachments.64
Of the problems encountered by chemical mortar units on Okinawa, shortage of ammunition was unquestionably the most serious. The 88th Battalion took in three units of fire and the 91st Company took in five on the basis of 100 rounds per unit of fire, at the ratio of 70-percent HE and 30-percent WP. After this initial supply was consumed, a shortage, which varied from limited to critical, prevailed for the balance of the operation. On at least four separate occasions, mortar companies had to reduce expenditures or cease firing altogether for periods of from a few days to two weeks. Rain and mud, particularly after May, bogged down ammunition resupply and made it difficult for the chemical mortars, as well as other supporting weapons, to keep up with the infantry. The over-all shortage of chemical mortar shell was partly a result of the higher priority of the European theater. But as in the case on Luzon, 35,000 of the 87,400 rounds of high explosive ammunition received from the zone of interior were in lots suspected of having defective fuzes. Indeed, a muzzle burst was reported by Company B of the 88th on 13 May, the date on which 14 men were listed as wounded in action. The Navy transferred 27,000 rounds of HE shell not
employed in amphibious support operations, but the use of much of this was “restricted to military necessity.” The average mortar company expenditures of approximately 335 rounds per day was made possible only by substitution of WP for HE shell, by the above Navy transfers, by dispatch of 50,000 heavy-weight M4 rounds from Hawaii, and by the replacement of all defective fuzes, shipped by high priority air shipment from Hawaii and the United States.65
Amphibious Employment of the 4.2-Inch Chemical Mortar
Before the War Department authorized the high explosive mission for the 4.2-inch mortar and before any chemical mortar units reached the theaters of operations, the CWS was developing doctrine for the use of the mortar in assault landings. Beginning in the summer of 1942 this doctrine was developed at the Amphibious Training Center, Camp Edwards, Mass., and continued at Camp Carabelle, Fla. (later Camp Gordon Johnston) . Overseas, the U.S. Assault Training Center in England advocated the use of 4.2-inch WP shell for smoke screens for assault landings except in the case of offshore winds, when only high explosives would be used.66 Elements of the 3rd Chemical Mortar Battalion sailed from North Africa for Sicily prepared to support the 3rd Division with mortars mounted on six assault craft, a measure made unnecessary with the attainment of tactical surprise.67
Despite these preparations in the European theater the amphibious employment of the 4.2-inch mortar occurred only in the Pacific. Colonel Unmacht first suggested the technique to Navy officers in July 1943 at the Makua, Oahu, demonstrations. The Navy liked the idea and played around with it for almost a year. The advantage of the mortar boat plan was that it provided assault troops with heavy effective fire during that period in the landings when they were most vulnerable—the time between the lifting of the naval bombardment and the establishment of supporting weapons on shore.
In a remarkable case of CWS-Navy cooperation, the kind which typified the activities of Colonel Unmacht on Oahu, there emerged a new type of craft, one armed with 4.2-inch chemical mortars. It was not born without difficulty. The Navy provided three LCTs for the project and later several LCIs. The latter, dubbed LCI(M) (the M for mortar) , were to become the standard mortar-landing craft combination.68
One of the principal mechanical difficulties in firing the 4.2-inch mortar from the deck of a ship was the development of a suitable mount. The Navy experimented with various devices including one which mounted the mortar solidly in the deck of an LCT. Fourteen rounds fired from the weapon were sufficient to shear the bolts holding the base cap cup to the deck. The mount finally adopted consisted of a wooden box reinforced with steel and filled with a mixture of sand and sawdust. Upon this mixture sat a wooden subbase, the top of which was notched to receive the spades of the base plate. These mounts proved adequate, although excessive firing, such as at Iwo Jima, caused them to break down.
The first attempt to get the mortar boats into action proved abortive. Favorably impressed with these vessels during seven tests again run at Makua in the spring of 1944, the Navy decided to use three of the 4.2-inch-mortar-equipped LCTs in the invasion of Saipan. These plans went awry during the assault rehearsal off Kahoolawe, one of the Hawaiian group. Each of the three LCTs was lashed to the deck of a landing ship tank, for the decision had been made for the smaller vessel to make the long journey to the scene of operations in this piggyback fashion. During an extremely heavy sea two of the LCTs broke their lashings and were washed overboard. The third LCT escaped this fate only to be destroyed at Pearl Harbor when its LST suddenly exploded. Fifty-nine people lost their lives in the resulting holocaust.69
Before the end of the Marianas campaign, the Navy revived the mortar boat project. This time the weapons were to be mounted on landing craft, infantry (LCI) , four of which were fitted out, each with three 4.2-inch mortars.70 One weapon was mounted forward in the center of the ship, the others were amidships, one on the port side
Firing 4.2-inch chemical mortars from the deck of an LST in the Pacific.
and one on the starboard. All fired forward, over the bow. Beneath the mortar mounts the deck was reinforced with steel plating. The two forward troop compartments served as magazines for mortar ammunition, a normal complement being 1,200 rounds. Maj. Leland E. Anderson of the 88th Chemical Mortar Battalion commanded the mortarmen who had come from diverse sources: 4 officers from the 88th, 12 enlisted men from the 91st Chemical Mortar Company, and 4 officers and 88 enlisted men from the 111th Infantry Regiment. Designated as LCI(M) Nos. 739, 740, 741, and 742, the mortar boats were earmarked for the campaign in the Palaus. The four boat crews prepared for the operation by test runs at the Makua site in the Hawaiian Islands and by participation in the invasion rehearsal at Guadalcanal.71
Palau Islands
The first combat employment of chemical mortar boats took place on 15 September 1944 in the Palau Islands.72 Led by Major Anderson, mortar boats 739, 740, 741, and 742 supported the III Amphibious Corps landings on Peleliu made by the 1st Marine Division. During the initial run on the island LCI(M)s, moving in at a speed of less than three knots, fired 100 rounds of high explosive ammunition from positions 3,000 to 1,300 yards offshore at the very slow rate of one round per mortar every two minutes. As the mortar boats drew closer, the range of the weapons was decreased by reducing the number of increments.73 This method of fire was sometimes known as Plan BAKER. Mortar fire covered the northern flank of White Beach for a depth of 200 to 300 yards, with only a few water bursts being observed. These supporting boats lifted their fire as friendly aircraft strafed the beach only to resume it from fixed positions 900 to 1,300 yards offshore. The mortars then placed harassing fire upon the dense woods, areas of defilade, and possible enemy observation posts and installations on the hill to the northwest. Good dispersion resulted from this fire, delivered at ranges varying between 2,100 and 2,610 yards, although the thick foliage and defiladed areas precluded effective observation. The employment of mortar boats from fixed offshore positions was often designated Plan CHARLIE.
A second mission at Peleliu began about an hour after the end of the first run and consisted of the bombardment of the same hill area northwest of the beach area, its rocky top by now a mass of rubble. Firing at ranges of 3,200 yards, each mortar delivered two rounds of high explosive shell a minute from more or less stationary positions 1,800 to 2,100 yards offshore. While winds and currents at Peleliu were not strong enough to cause excessive drift, the little movement which did occur made precise firing difficult. Radar ranges taken by LCI(M) 741, the flagship, as well as visual cross-bearings and fall of shot observations, helped to fix the ship positions and to determine ranges as the vessels drifted or maneuvered. In any event, the resulting dispersion was not detrimental to the general mission of laying down
area harassing fire. Enemy mortar fire during the two runs proved ineffective, most rounds falling short.
Firing from a moving boat had little effect upon the accuracy of the mortar. In rough seas lateral, but not vertical, accuracy was impaired. And the latter was the more important factor because of the possibility of hitting friendly troops as they advanced inland.74
Two days later, on 17 September, the same four mortar boats supported the 81st Division assault on the island of Angaur, also in the Palaus. Instead of executing Plan BAKER immediately, as had been done at Peleliu, all craft fired on abbreviated Plan CHARLIE-6 to 10 rounds per mortar per minute for 7 minutes from positions 2,400 yards offshore. The group of gunboats then moved toward shore at a speed of four knots. It took Io minutes to come within 1,000 yards of the beach, during which time each of the mortars fired at the rapid rate of 20 rounds per minute. Excessive noise made the commands of the fire control officer virtually inaudible while smoke did much to hinder observation. Despite these handicaps most of the 2,345 rounds landed in the target area and inflicted extensive damage.
On the following day infantry troops on shore, pinned down by rifles and machine guns, called for supporting fire. There was time for only 2 runs, one of 6 and the other of 8 minutes, at speeds of 4 and 3 knots, respectively. The target area, located on the northwest end of the island, varied in width from 500 to 850 yards and extended from the shore to a depth of 900 yards. At an average firing rate of 5 rounds per mortar per minute, 830 rounds fell in the area. Mine fields prevented the mortar boats from approaching closer than 1,500 yards from shore, but the effectiveness of the mortar barrage was such that 3 minutes after it had been lifted the troops, previously pinned down by enemy fire, encountered no opposition on advancing into the heavy woods.
At the end of the Palau operation CWS officers recommended that mortars on boats making the run toward the shore maintain a constant elevation of 1,000 mils with traverse dependent upon the course of the craft. They also suggested that mortar fire be kept within 400
yards of the assault troops and that mortar ships maintain an offshore range of beween 3,200 and 2,000 yards as a precaution against enemy fire. The latter recommendation was disregarded; subsequently, mortar ships came within Soo yards of the shore. Suggestions about the more effective installation of the mortars on the ships were either not adopted or proved to be without merit.75
Leyte Gulf
Two groups of mortar ships supported the landings at Leyte Gulf on 20 October 1944. Each group was composed of four LCI(M)s, with two LCI (A) ‘s serving as ammunition ships. Maj. Richmond H. Skinner, CWS, exercised over-all command of mortar firing personnel of the groups. Men from the 98th Infantry Division stationed at Hawaii manned all twenty-four mortars in the two groups and fired in support of the 7th and 96th Divisions under XXIV Corps in the Leyte landings made near Dulag. From the date of departure from Manus Island on ur October until the objective was reached, these new mortar crews received training in firing methods and commands.
One of the groups (it was known as Group 2) executed Plan BAKER at Orange Beach 2 as mortar boats moved in at a speed of II/2 knots, firing from 2,200 to 400 yards offshore and expending about 480 rounds of HE in 20 minutes. A slow rate of fire of two rounds per gun per minute was maintained while the range was gradually decreased from 2,600 to 740 yards. Twelve hundred yards from the shore enemy mortars or howitzers straddled the mortar boats without causing casualties or damage. The weather was ideal and the sea relatively calm.
After execution of Plan BAKER these mortar boats fired from fixed positions (Plan CHARLIE) on enemy positions in the ravines and on reverse slopes of the Labiranan Head Ravine and Catmon Hill area, silencing the Japanese guns which had been plaguing the troops on the beaches. According to one Navy observer, this mission, completed without observation from computed data and fired at distances from 1,000 to 1,900 yards offshore, proved accurate beyond expectations. Later, Group 2 moved back to the transport area, twelve miles to the
rear, for resupply. It received no further missions that day. Thereafter, until they withdrew on the morning of A plus 5, the mortar boats of this group used smoke pots to screen the large vessels from air raids during the hours of both morning and evening twilight.
On the morning of the attack on the Leyte beaches the other group of mortar boats (known as Group 3) fired on targets south of Yellow Beach as far as the mouth of the Daguitan River near the town of Dulag. Spaced from so to 75 yards apart the mortar boats began firing 1,500 yards from shore and continued as they slowly moved in to a position 400 yards from the beaches. This bombardment blanketed an area Boo yards wide and 900 yards deep. Fifteen minutes after this beach shelling phase, the mortars began firing on call. Within the next five hours infantry requests for support resulted in the expenditure of almost 4,500 rounds. The ships slowly drifted to the left directing their fire on enemy targets on the south bank of the Daguitan River and on the approaches of a bridge across that river, an effort which drove enemy tanks from the road leading to the bridge.
Both mortar boat groups received written commendations from the leaders of the flotillas which they supported, as well as from the commanders of Amphibious Groups 3 and 6. Admiral Forrest B. Royal, commander of Group 6, stated: “The performance of LCIs equipped with 4.2” Army mortars was excellent. The mortar fire was delivered in a rapid, accurate, and effective manner.” Admiral Royal compared the effectiveness of the mortar ships and the rocket ships.76 While praising the “highly successful accomplishments” of both weapons, he pointed out that the rocket ships were of no further use after their single crash concentration because they were unable to reload in time to continue covering the assault waves. On the other hand, the mortars could fire without letup.77
Lingayen Gulf
For a short time after the recall of the mortar boats from the Leyte fighting, future plans for their use were hazy because of the lack of
information regarding the Luzon operation.78 Both groups did proceed to New Guinea to pick up men from the 98th Chemical Mortar Battalion, a step made necessary when four landing craft, infantry, which had served as ammunition carriers during the Leyte action, were converted to mortar boats. All mortar craft participated in the mid-December training exercise in Huon Gulf, which simulated the landings that were to take place at Lingayen Gulf, Luzon.
As it turned out, three separate mortar boat groups supported the Sixth Army landings on Luzon. One of these was Task Unit 79.8.1, composed of six LCI(M)s and commanded by Lt. Comdr. G. W. Hannett and accompanied by Maj. Richmond Skinner. A second group was formed from the converted ammunition carriers, with mortar-men from the 98th Chemical Mortar Battalion. A third group of three LCI(M)s had its mortars manned by marines, trained by and under the supervision of a detachment from the 98th Chemical Mortar Battalion.79
The six mortar boats of Task Unit 79.8.1 supported the XIV Corps landings on the beaches of Lingayen Gulf and then stood ready to furnish fire on call of the 185th Infantry, 40th Division, in its movement inland. The mortar boats were to be ready for any special mission that might arise, as well as to smoke the transport areas during the hours of morning and evening twilight.
The fire plans for support of the assault wave were quite elaborate, including time, range, and rate of fire for the period beginning thirty minutes before the assault until fifteen minutes after the troops had landed. White phosphorus ammunition was put aboard to be used only in case of an onshore wind. General control of the mortar ships was in the hands of the task group and task unit commanders, but individual vessels maintained the responsibility for engaging specific targets. Each mortar ship carried 1,200 rounds of HE, too rounds of WP, as well as an ample supply of 20-mm. ammunition. Training of the mortar crews continued even while en route to the objective. Navy men received instruction in the handling of the mortars in the event that casualties would bring a need for extra hands.
S-day for Luzon, 9 January 1945, found climatic conditions
favorable, with a mild offshore wind and visibility ranging from fifteen to twenty miles. The swell of the sea caused some difficulty with landing operations but did not seriously affect the mortar missions. Shortly after 0600 the six mortar ships broke off from the main body, maneuvering in zigzag fashion through the armada of support ships to their initial positions 2,500 yards from shore. A few minutes later, an enemy suicide bomber swooped down in attack. The Japanese plane itself inflicted no damage, but five men from an LCI(M) received wounds from a 20-MM. shell fired at the enemy by another vessel in the formation. At 0845 the six mortar ships moved into their attack positions; fifteen minutes later they began their scheduled fire.
The LCI(M)s moved forward, blanketing the beaches to a depth of almost 350 yards with accurate and devastating fire. As the craft approached the shore the number of propellant charges on the mortar shells was progressively decreased. Precise ranges were determined by radar on several of the LCI(M)s and passed on to the others by prearranged visual signals. The only return fire came from enemy mortars whose shells fell boo yards offshore. Upon reaching a position 400 yards from shore the mortar boats laid to, but continued their fire on the beaches as the first wave of assault troops passed through. It was now 0934, the time when small arms fire support on the gunboats and mortar ships ceased; naval gunfire had been lifted when the first wave reached a position Boo yards from shore.
The mortar crews continued their support from this close-in position. At one stage a radio message was misinterpreted and four LCI(M)’s ceased fire. Thick smoke precluded visual signals and fire was not resumed until several minutes later, when the noise and smoke had abated. During the initial phase of the assault the mortar unit expended 3,345 rounds of high explosive ammunition. Because of an offshore breeze, only seven rounds of WP were fired, this for ranging in at a position 2,600 yards from shore.
According to plan, the mortar ships ceased fire at 095 i and proceeded obliquely to the port to take up positions some 800 yards offshore where they could fulfill the second part of their mission. Although the mortar boats stood ready to support the 185th Infantry shortly after 1000 on S-day, they received no calls for fire because the infantrymen pushing inland to the Agno River encountered no enemy opposition. The mortar group spent the night of S-day anchored just off
the mouth of the river, and next morning placed area fire on enemy troops which, according to the shore fire control party, effectively routed the opposition. Some of the LCI(M)s replenished their ammunition supply from an LST standing by with a reserve of 4.2-inch shells.
From S plus 1 until S plus 8 the group of mortar ships provided twilight smoke concealment and escort service for the Liberty and Victory ships in the San Fabian transport area, a mission which terminated operations of Task Unit 79.8.1 at Luzon. During this period its mortars fired more than 5,000 rounds of 4.2-inch ammunition; the 20-MM. guns of the unit expended almost 7,700 rounds during antiaircraft operations.
The second group of mortar boats, the four converted from the ammunition detail, supported I Corps landings east of Dagupan. As in the case of Task Unit 79.8.1, these LCI(M)s provided the ships in its vicinity with the concealment of smoke during the twilight hours so susceptible of enemy air attack. On S plus 3 the group went out of action, its mortar crews returning to their parent unit, the 98th Chemical Mortar Battalion. As far as casualties were concerned this small unit fared rather badly; on S plus I an enemy E-boat torpedoed the radar equipped flagship with a loss of 2 officers and 2 enlisted men.80
Group 78.1.8, the smallest of the three mortar boat units, also supported the I Corps landings near Dagupan. From positions within 3,000 yards of the beach, each of the group’s three mortar boats fired about too rounds of high explosives onto a road and railroad track just in from the shore. Advancing to within 1,000 yards of the beach, the mortar boats engaged unspecified targets on both the forward and reverse slopes of the low-lying hills, then retired to await call fire from the 98th Battalion. No enemy fire was received from the beach. On S plus 3 this group shelled a group of the enemy and the railroad station south of Damortis.81
Vice Adm. Thomas C. Kinkaid, in command of the Lingayen landings, was especially pleased with the work of the mortar boats, reporting
that they were more effective for beach neutralization than were escort carrier-based planes.82
Iwo Jima
The success of the mortar ships in Pacific assault operations prompted the Navy to increase the number of this type of vessel.83 Some were acquired and equipped in California, others at Pearl Harbor. The men who were to fire the mortars on these boats were exclusively Navy men, trained in Hawaii by a cadre from the 189th Chemical Mortar Company under the direction of Lt. Col. Joseph E. Atchison. Naturally, the Navy crews had much to learn; many had never seen the mortar before. To some this lack of knowledge meant apprehension of the weapon, to others it meant incorrect employment, with damage and danger as a consequence. There were several examples of a second shell being placed in the mortar barrel on top of a misfire and one case where the crew attempted to jam in three rounds. The training in Hawaii, which included two test runs off the coast of Kahoolawe, went a long way in correcting these inadequacies.
On 22 January 1945 the fourteen mortar boats left Pearl Harbor for Iwo Jima where they were joined by the LCI(M)s which had seen action at Lingayen Gulf. Four CWS officers from the 189th Chemical Mortar Company accompanied the Pearl Harbor contingent, attached for the operation to the mortar group—five units of six ships each.
On the morning of 19 February 1944 the 4th and 5th Marine Divisions landed on the beaches of the island of Iwo Jima in the face of the heaviest enemy beach resistance since Tarawa.84 The bombardment of the island that preceded the attack was the heaviest of the Pacific war, one that benefited from the experiences of the island assaults that had taken place before. Three of the five mortar units, Numbers 1, 2, and 5, took part in the actual assault phase.
From H-hour minus 3 5 until H-hour minus 1o the mortars on these vessels expended 3,240 rounds to bombard specific area targets on the slopes of Mount Suribachi, the 5 50-foot extinct volcano which dominated the southern end of the island. These mortar groups used a maneuver sometimes described as Plan ABLE. In this plan five LCI(M)s of a mortar group moved counterclockwise in an elliptical pattern around the sixth vessel, which served as the reference point. Each ship fired only during the period of the run when it was pointed toward the target area. The advantage of this maneuver was the attainment of the high degree of accuracy needed for interdictory fire, accuracy which could not be realized from the decks of sporadically moving ships attempting to maintain a stationary position.
At H-hour Units 2 and 5, proceeding in columns, entered the boat lanes from the west, turned shoreward, formed a line parallel with the sixth wave, and followed it toward the beaches. Reaching a position 2,000 yards from shore, the mortars began firing at a rate of 6 rounds per minute and at a constant range of 3,200 yards. Stopping 1,000 yards from the beaches the mortar ships, now 200 yards apart, maintained fire on a line 1,800 yards inland until H plus 60, when they joined Mortar Support Units 3 and 4 in the rear to repair the damage sustained by the mortar mounts and await further assignment. Group 1, still employing the elliptical maneuver of Plan ABLE, resumed action at H plus 10 with almost four hours of neutralization fire. When this mission terminated Group 1 joined the other units in the rear, thus marking the end of mortar boat support during the assault landings at Iwo Jima.
After this first day the LCI(M)s, with but few exceptions, fired only night-time missions of harassment and interdiction.85 The small size of Iwo Jima (its surface area is only 7½ square miles) and its triangular shape made sea support of land operations singularly appropriate. Mortar Units 2 and 5 complied with requests from the forces on land for harassing mortar fire during the first night on shore. Stationed off the eastern and western side of that point of the island tipped by Mount Suribachi, the two mortar units placed fire on the area between the opposing forces to prevent large-scale counterattacks by the enemy. These missions saw the first significant use of white phosphorus shell; as an aid to observation during these hours of
darkness every fifth round was WP. On subsequent nights mortar units fired similar missions using Plan ABLE and also Plan CHARLIE. Because of heavy counterbattery fire received by the mortar groups they were sometimes directly supported by heavier vessels. The destroyer, USS Shannon, for example, covered Mortar Unit 2 as the LCI(M)s delivered harassing fire on the night of 23 February.
Three mortar boat groups departed on 26 February, and the two that remained reorganized into 5-boat units. Thereafter this sort of support gradually decreased until 3 March, by which time all mortar boats had been recalled. During these last days individual LCI(M)s provided direct daylight support to shore battalions designated by the Headquarters Landing Force.
Ammunition expenditure of all mortar boats at Iwo Jima came to about 60,000 rounds, of which 20 percent was white phosphorus. The resupply of mortar ammunition from LST to LCI(M) in a fairly rough sea was not always an easy matter. Occasionally the boxes of shell dropped a substantial distance to the deck of the mortar boat, a circumstance which spoke well for the safety feature of the mortar shell fuze. Weapon breakage in this operation caused little alarm although the heavy firing frequently broke down the mortar mounts, taking the weapon out of action for the extent of the mission. Iron straps welded along the sides of the mounts eliminated some of this weakness. Sometimes it was necessary to place bands over the subbase of the mortar to keep it from jumping out of the mount. From all accounts, the mortar crews performed in an exemplary manner; Rear Adm. Harry W. Hill of Amphibious Group 2 termed the successful use of “mortar gunboats” in the early phases of the assault “one of the outstanding features of the operation.”86 According to CWS sources, the Marine Corps expressed its enthusiasm for massed fire from mortar boats during the early days of the landings.87
Operations in the Ryukyus
CWS-trained Navy crewmen manned a total of 60 LCI(M) ‘s which supported Tenth Army in the Ryukyus Campaign. Six days before the main assault of Okinawa, two 6-boat mortar groups supported the diversionary effort against Kerama Retto made by the 77th Infantry
Division. On 1 April 1945 the XXIV Army Corps and the III Amphibious Corps successfully carried out the main landings on the western coast of Okinawa. Prior to H-hour on that morning seven groups of LCI(M)s, each comprised of six boats, lined up parallel to the beach behind the assault troops. Each LCI(M) carried 1,000 rounds of HE and 200 rounds of WP. Using Plan BAKER, the 42 boats moved through a calm sea at about one knot, their 126 mortars opening up at a point 1,600 yards from shore at a rate of Jo rounds per gun per minute. Firing over the heads of advancing troops the mortars, in less than an hour, placed about 28,000 rounds on a beach area 1,000 feet deep and 5½ miles wide. The mortar boats themselves received no enemy fire.
Another group of LCI(M)s supported the 2nd Marine Division’s L-day feint against the southeast coast of Okinawa. Subsequent 77th Division landings at Ie Shima on 16 April received the support of two groups of mortar boats, while three days later a single group fired for the ruse landing made by the same division in southern Okinawa. From 7 May until 27 June LCI(M)s, in support of Army and Marine troops, shelled the city of Naha and enemy installations in the vicinity of the capital.88
The amphibious use of the 4.2-inch mortar was one of the major contributions of the CWS to the Pacific war. The mortar boat proved extremely effective for close infantry support just before, during, and immediately after amphibious landings. It was then that the assault troops, running the gantlet of enemy fire while attempting to secure a foothold on the beach, benefited from all the support fire that could be provided. The effectiveness of the mortars in this support is best reflected in the steady increase in the number of mortar boats committed to Pacific assault operations. Only four LCI(M)s saw action in the Palau fighting in September 1944; seven months later a total of sixty supported Tenth Army operations in the Ryukyus.