Part Five: The Shimbu Group and the Visayan Passages
Blank page
Chapter 20: American Plans for Post-Manila Operations
While XI Corps was concluding the operations to secure Manila Bay, Sixth Army had turned its attention to completing plans for the destruction of the Shobu and Shimbu Groups, the two largest concentrations of Japanese strength left on Luzon after Sixth Army had brought the Kembu Group and the Manila Naval Defense Force under attack.1 Sixth Army’s offensives against the Shobu and Shimbu Groups were slow to gather momentum, although the necessity for launching such offensives had been obvious from the beginning of the campaign.
By early February Sixth Army’s I Corps, poised along the northern edge of the Central Plains, and XIV Corps, smashing its way into Manila, had attained positions from which they could strike against the Shobu and Shimbu Groups. If Sixth Army postponed for long the I Corps offensive against the Shobu Group, that northern Japanese force would have ample time – too much time – to ready its defenses and gather the supplies of all types from the Cagayan Valley necessary to a protracted stand in the mountains of north Luzon. Each day that passed before attacks against the Shobu Group began would render I Corps’ ultimate task more costly and time consuming. By the same token, General Krueger knew, Sixth Army would find it difficult if not impossible to completely assure the security of the Manila Bay region until XIV Corps could launch an attack against the Shimbu Group concentration in the mountains north and northeast of Manila. Of urgent importance to American development of the Manila area was the dismal fact that the Shimbu Group controlled the main sources of Manila’s water supply.
From the beginning of the Luzon Campaign, General Krueger had known that he would have insufficient resources to undertake simultaneous, concerted attacks against all the Japanese concentrations on Luzon, no matter how desirable
such a course of action might appear to him. His earliest plans for operations against the Shobu Group, for example, called for the employment of at least five, possibly six, divisions in concurrent offensives in northern Luzon.2 As of early February, however, he could not provide I Corps with such strength without stripping XIV and XI Corps of the forces required to secure the Manila Bay region – a step he obviously could not take. However, Krueger did expect that, with the exception of certain elements of the 24th Division, he could retain on Luzon almost all the troops deployed on the island as of early February. He anticipated that with these units, plus reinforcements scheduled to reach Luzon later in the month, he could proceed fairly rapidly with the destruction of the Shobu and Shimbu Groups. For the purpose of mounting attacks against the two Japanese groups he would also redeploy, as they became available, the divisions he had already committed against the Kembu Group and the Manila Naval Defense Force.
General Krueger was not to realize his expectations. During the first week of February General MacArthur decided that Sixth Army could secure the most important strategic objective of the Luzon Campaign, the Central Plains-Manila Bay region, with considerably less strength than theater planners had originally contemplated. Furthermore, MacArthur felt that base development projects on Luzon – not only for the support of Sixth Army operations but also for the support of subsequent offensives throughout the Pacific – would require Sixth Army to commit much of its strength to operations other than offensives aimed at the quick destruction of the Shobu and Shimbu Groups. Attacks against these two Japanese forces, the theater commander informed Krueger, should assume secondary importance in plans for operations following immediately upon the clearance of the Manila-Manila Bay area:
It is possible that the destruction of enemy forces in the mountains of north and east Luzon will be time consuming because the nature of the terrain will probably channelize operations and limit development of full power. Initially, hostile forces should be driven into the mountains, contained and weakened, and our principal effort devoted to areas where greater power may be applied.3
MacArthur felt that development of a safe, short shipping route through the central Philippines – that is, through the Visayan Passages – was an urgent requirement for the establishment of large air, naval, and logistic bases on Luzon. Ever since 9 January, Allied shipping had been moving into Philippine waters at Leyte Gulf, sailing thence southwest through Surigao Strait and the Mindanao Sea into the Sulu Sea. Following the route employed by the Lingayen Gulf invasion convoys, the shipping then turned north to pass west of Mindoro Island, into the South China Sea, and finally up the west coast of Luzon. The Southwest Pacific Area could save considerable time and, ultimately, ships if it could shorten this roundabout route to one beginning at San Bernardino Strait, which separates Samar Island, north of Leyte, from the southeastern tip of Luzon. Sailing through San Bernardino Strait, Allied vessels could move
into the Sibuyan Sea, sail northwest through the Verde Island Passage between northern Mindoro and southern Luzon, move on into Manila Bay, This second route saved some 500 nautical miles and was less hazardous for small vessels than the open, often stormy waters of the Sulu and South China Seas.
General MacArthur knew that the Japanese maintained coveys of suicide craft at various hideouts along the southern coast of Luzon and the southern shore of the Bicol Peninsula, southeastern Luzon. He also had reason to believe that the Japanese had emplaced coast artillery on the south coast of Luzon, the Bicol Peninsula, some of the small islands of the Visayan Passages, and northern Samar. His forces would obviously have to clear all these areas before he could make use of the water passages through the central Philippines. Accordingly, MacArthur directed Sixth Army to clear southern Luzon and the Bicol Peninsula, and simultaneously ordered Eighth Army to capture the smaller islands and the northern portion of Samar.
Another objective of post-Manila operations, MacArthur informed Krueger, was the early opening of Batangas Bay, on the south-central coast of Luzon, to Allied shipping. GHQ SWPA had drawn up plans for extensive base and port development at Batangas Bay. The theater intended to locate a large staging base for the invasion of Japan along the bay’s shores; it planned to set up in the same region, which lay comfortably distant from the crowded Manila metropolitan area, a major hospital center to take care of casualties expected during the invasion of Japan; and, among other things, theater engineers planned to establish a landing craft assembly plant at Batangas Bay. GHQ SWPA also planned base development of lesser magnitude for Balayan Bay, west and northwest of Batangas Bay.
Finally, General MacArthur pointed out to Krueger, development of greater cargo discharge capacity at all existing and potential bases on Luzon was a continuing requirement. This requirement, MacArthur realized, could be largely met by planned logistical development at Manila and Batangas Bays, but he believed it necessary to establish additional port facilities along the northwestern coast of Luzon. The theater had to undertake such development – the first of it to be located at San Fernando, La Union, at the northeast corner of Lingayen Gulf – not only to ease the existing burden upon the overtaxed facilities at Lingayen Gulf but also to support subsequent operations of Sixth Army in northern Luzon and to provide ports of entry for matériel to be employed in the construction and use of airfields that GHQ SWPA intended to establish along Luzon’s northwestern coast.4
Thus, in early February, General MacArthur limited Krueger’s freedom of action by directing him to execute operations that would make it impossible for Sixth Army to deploy effectively its principal strength against the main bodies of the Shimbu and Shobu Groups. About the same time, the theater commander put additional restraints upon
Krueger by detaching troops from Sixth Army. With Leyte, southern Samar, and Mindoro already cleared, and with the Luzon Campaign well along, MacArthur, anxious to reassert American hegemony throughout the rest of the Philippines, decided to speed the destruction of major centers of Japanese resistance in the bypassed central and southern islands of the Philippine archipelago. Theater combat strength was by no means inexhaustible, and the initiation of the campaign in the southern Philippines, MacArthur knew, would require some reorientation of effort from Luzon. The theater commander realized that this redirection of effort would slow the conquest of Luzon, but that was a penalty he was willing to accept.
Having made the decision, MacArthur proceeded to implement it by reducing the strength he had originally allocated to Sixth Army for the prosecution of the Luzon Campaign. First, on 7 February, the theater commander informed Krueger that the 41st Infantry Division, already loaded for shipment to Luzon, would be given to Eighth Army for operations in the southern Philippines. Then, in rapid succession, Krueger received in early February the unwelcome news that the 24th Infantry Division’s 34th RCT, which had been operating with XI Corps, would soon have to go back to Mindoro to make ready for participation in Eighth Army operations in the southern Philippines; that the two battalions of the 24th Division’s 19th Infantry and other 24th Division units that had been attached to the 11th Airborne Division south of Manila would have to be sent back to Mindoro immediately; that the 503rd Parachute RCT would soon have to be redeployed from Corregidor to the southern islands; and that the entire 40th Infantry Division would be withdrawn from Luzon to take part in the Eighth Army’s campaign in the southern Philippines. Supporting combat and service units would also depart for the south, and Sixth Army would not receive other combat and service units it had expected to employ on Luzon. Next, MacArthur informed Krueger that the 37th Infantry Division, once it had completed operations in Manila, would be tied down for perhaps two months as a garrison force for the metropolitan area.
Instead of the eleven divisions and four separate RCTs Krueger had expected to employ on Luzon, he would have only nine divisions (one of which would have to remain in the Manila area for some time) and two separate RCTs. In all, taking into account artillery, armored, and service units that were also redeployed from Luzon to the southern Philippines or were stricken from the Luzon reinforcement list, Krueger lost the equivalent of three divisions permanently and a fourth, the 37th, temporarily.5
The combined impact of MacArthur’s operational and redeployment directives forced General Krueger to undertake a
wholesale reshuffling of units already committed on Luzon, to make careful plans for the future employment of forces left on the island, and to make sweeping changes in tentative plans for operations all over Luzon. Krueger’s first problem was to find a replacement for the 40th Infantry Division, which was fighting against the Kembu Group west of Clark Field.6 Sixth Army had one easy solution to this problem – to replace the 40th with the 33rd Infantry Division, which reached Luzon from New Guinea and Morotai on 10 February.7 However, Krueger knew that the tired 43rd Division and the 158th RCT needed some rest and rehabilitation after their hard fighting in the Damortis-Rosario region. Having learned from GHQ SWPA that the 40th Division would not have to leave Luzon until early March, Krueger decided to use the 33rd Division to relieve the 43rd Division and the 158th RCT. Then, after two weeks’ rest, the 43rd would move south to replace the 40th Division in the Kembu area. The 158th RCT, after its rest, would be employed in southern Luzon.8
Simultaneously, Krueger decided that he would use the 11th Airborne Division – which was still fighting in the area immediately south of Manila in early February – in southern Luzon for operations designed to clear the northern shores of the Visayan Passages and to open Batangas and Balayan Bays. He estimated that the 11th Airborne Division and the 158th RCT would be ready to move against southern Luzon by the first week of March. Together, the two units would not attain the strength of a standard infantry division, but Krueger was unwilling to assign any more forces to the campaign in southern Luzon immediately, since he believed it necessary to initiate at least a limited offensive against the main body of the Shimbu Group in the mountains east and northeast of Manila before the end of February. Unless he mounted some sort of an attack against the Shimbu Group, Krueger felt he would be unable to assure the security of the vital Manila Bay region, because he estimated that the Shimbu Group possessed a strong offensive capability that it might exercise at any time.
With all the other operations Sixth Army already had planned or under way, Krueger found it difficult to assemble sufficient strength to launch even a limited offensive against the Shimbu Group. By mid-February the only units he had not already committed to specific courses of action that demanded continuous attacks against Japanese defensive positions were the 2nd Cavalry Brigade of the 1st Cavalry Division, just finishing the task of clearing Manila’s northeastern suburbs, and the small 112th Cavalry RCT, which was protecting XIV Corps’ long line of communications down the eastern side of the Central Plains. These two units were patently of insufficient strength to undertake an attack against the Shimbu Group, which Krueger’s
G-2 Section, in a gross underestimation, reckoned had nearly 20,000 troops in the hills immediately east and northeast of Manila.9 Therefore, the Sixth Army commander reluctantly decided to redeploy the 6th Infantry Division (less the 1st RCT, which was already operating on Bataan under XI Corps) south from the I Corps sector to provide XIV Corps with adequate strength to move against the Shimbu Group. Thus depriving I Corps of strength required for an early, concerted attack against the Shobu Group in northern Luzon, Krueger realized that I Corps would have to strike out against that northern Japanese force with three divisions rather than the minimum of five that he had originally planned the corps would use. The Sixth Army commander knew that he was delaying the ultimate destruction of the Shobu Group, but General MacArthur’s directives had left Krueger no alternative. He had to carry out MacArthur’s orders with the means the theater commander had left him.10
At the same time that Krueger started the bulk of the 6th Infantry Division southward from the I Corps area, he directed XI Corps to relieve the division’s 1st RCT on Bataan and dispatch it eastward to rejoin the rest of the division for the XIV Corps drive against the Shimbu Group. Finally, better to enable XIV Corps to concentrate its efforts against the Shimbu Group and Japanese forces in southern Luzon, Krueger eased the corps’ administrative and tactical burdens by transferring responsibility for the further conduct of operations against the Kembu Group to XI Corps.11
Thus, as of late February, when Krueger could foresee the successful completion of operations to secure the Manila-Manila Bay area, XIV Corps could make preparations to send the 6th Infantry Division and the 2nd Cavalry Brigade against the Shimbu Group’s principal concentrations. XIV Corps was also in a position to direct the 11th Airborne Division and the 158th RCT to move into southern Luzon, but until early March the corps would have to employ the 37th Infantry Division and the 1st Cavalry Brigade to reduce the last Japanese resistance in Manila, while the 112th Cavalry RCT would continue to operate along the corps’ line of communications. To begin its attacks against the Shobu Group in northern Luzon, I Corps had left the 25th, 32nd, and 33rd Infantry Divisions. XI Corps had under its control the 38th Infantry Division, the 40th Infantry Division (which it was soon to lose), and the 43rd Infantry Division. The 503rd Parachute RCT and the 24th Division’s 34th RCT would remain under XI Corps command until early March, but would then have to leave for the southern Philippines. General Griswold, commanding XIV Corps, was not, of course, worried about the strength of other corps on Luzon – his worry was to find the strength necessary to execute all the tasks Sixth Army had assigned him.