Chapter 12: Breakout and Pursuit
Tactical Developments
For most of the month of July the First U.S. Army had been preoccupied with a series of attacks designed to win additional maneuver space and to gain the more favorable terrain—the higher ground between Coutances and St. Lô—considered essential as a line of departure for a general offensive. These attacks were halted on about 18 July, at which time the front line lay just north of the Lessay–Périers–St. Lô highway. This was somewhat short of the objective assigned early in the month. Nevertheless, the time now appeared propitious to launch an all-out attack to break through the enemy defenses in Normandy as a prelude to a drive into Brittany. Postponed for a week because of unfavorable weather, Operation COBRA was finally launched on 25 July. Following an air bombardment on an unprecedented scale, the heavily reinforced VII Corps (four infantry and two armored divisions) initiated the offensive on a narrow front between Périers and St. Lô. (Map 15) In the face of devastating blows from the air and on the ground the enemy lines soon gave way. On the second and third day of the attack telling strokes by the VII Corps ripped an ever-widening breach in the enemy’s positions. Meanwhile, beginning on 26 July, the attacks were joined first by the VIII and V Corps, and then by the XIX Corps. On 28 July armored elements of both the VIII Corps (which also had a strength of four infantry and two armored divisions) and VII Corps converged on Coutances. They captured the town on the same day, completing the major part of the COBRA operation.
Taking full advantage of the enemy’s disorganization,. the VII Corps turned southward and together with the VIII Corps vigorously pressed the attack. By 31 July the Americans had captured both Granville and Avranches, thus unhinging the enemy’s left flank and opening the door into Brittany.
On 1 August, with a total of eighteen U.S. divisions available on the Continent, the 12th Army Group became operational under the command of General Bradley, taking control of both the First Army (eleven divisions on 1 August), now commanded by General Hodges, and the Third Army, which also became operational at this time under the command of General Patton. The Third Army initially consisted of the VIII Corps, which was taken over in place, and the newly arrived XV Corps, and had seven divisions at its disposal.
The attacks continued without interruption on 1 August. While the First Army drove back the enemy’s center southeastward toward Vire, the Third Army struck southward through the Avranches gap with the mission of clearing Brittany. By 3 August Rennes was captured, and armored
Map 15: Tactical Progress
units had already knifed more than 80 miles into the heart of the peninsula, reaching Loudeac.
At that date the enemy still presented a cohesive defense in First Army’s sector and offered stubborn resistance in the vicinity of Vire. South of the Selune River, however, the enemy’s defenses had been completely shattered by the breakout at Avranches, and resistance was for the most part uncoordinated, with some units in flight. In addition, warm, clear weather
[Remainder of map merged onto previous page]
enabled the Allied air forces to take full advantage of their superiority, providing continuous cover to friendly armored columns and relentlessly attacking all enemy movements and concentrations. Furthermore, the enemy had already denuded Brittany of all its mobile units, and a strongly organized French resistance now came forward to hasten the enemy’s disintegration in the peninsula. Consequently there was little to impede the advance of U.S. forces in the area.
This very favorable combination of circumstances led to the first major alteration in the tactical plan. On 3 August the Third Army was directed to employ the minimum forces necessary to clear the Brittany peninsula and protect the southern flank along the Loire, and to make its main effort eastward to the Mayenne River. In accordance with these new instructions the XV Corps drove eastward, capturing the city of Mayenne on 4 August and Laval on the following day. Meanwhile the VIII Corps continued to push westward in Brittany. By 5 August the Quiberon Bay area was almost completely cleared and St. Malo was under attack.
Faced with the inviting prospect of delivering a decisive blow to German forces west of the Seine the 12th Army Group commander on 6 August directed the Third Army to continue its eastward drive to secure crossings over the Sarthe in preparation for an advance to occupy the Chartres plain and close the Paris–Orléans gap between the Seine and the Loire. Motorized infantry and armor accordingly pushed beyond the Mayenne, and on 7 August advanced to within twelve miles of Le Mans. By that time VIII Corps units had overrun most of the Brittany peninsula and prepared to invest the major ports, including Brest and Lorient. In the south the Third Army was reinforced by an additional corps (the XX), which took over the protection of the southern flank, twenty to thirty miles north of the Loire.
On the same day, 7 August, in a desperate attempt to sever the narrow Avranches corridor and restore a cohesive defense line anchored on the coast, the enemy launched a violent counterattack against the First Army westward from Mortain, employing many armored units. While the enemy persisted in his attacks for several days, attempting to isolate the Third Army, this threat was not considered serious enough to alter the latter’s mission. In fact, it was decided to capitalize still further on the enemy’s weakness and disorganization in the south and his deep commitment at Mortain without awaiting the outcome of the action on First Army’s front. The spectacular advances of General Patton’s forces appeared to offer the glittering prospect of trapping and destroying the entire German Seventh Army west of the Seine. On 8 August, therefore, in accordance with instructions from 12th Army Group, the Third Army captured Le Mans and then directed its main effort north toward Argentan while the 21 Army Group attacked southward toward Falaise in a huge double envelopment of the German forces. Armored. elements of the XV Corps reached Argentan on 13 August, where the advance on the southern edge of the pocket was halted on instructions from General Montgomery. The First Canadian Army met determined enemy resistance in the vicinity of Falaise. and the trap was not closed until 19 August, at Chambois, only a few miles northeast of Argentan. The delay enabled the enemy to withdraw considerable forces, although the Allied air and ground forces inflicted heavy losses in personnel and even more severe losses in matériel.
As early as 14 August, meanwhile, taking advantage of the enemy’s mounting confusion, the Third Army was ordered to resume the advance eastward. Leaving elements of the XV Corps on the southern edge of the pocket at Argentan to be taken over by First Army, the Third Army reinitiated its attacks eastward, with the XV Corps driving on Dreux, the XX Corps driving on Chartres, and the newly arrived
XII Corps advancing on Orleans. These objectives were captured within two days, and on 19 August, as Allied forces were closing the gap at Chambois, the Third Army established a bridgehead across the Seine at Mantes-Gassicourt, thirty miles below Paris. Leaving British units to mop up the encircled enemy forces in the Argentan–Falaise pocket, the First Army now also moved eastward and on 23 August took over the Mantes-Gassicourt bridgehead and the XV Corps and started across the Seine. South of Paris other Third Army units pressed eastward and forced additional crossings near Melun and Fontainebleau on the 24th.
Meanwhile, between 250 and 350 miles from the scene of these dramatic events, the battle continued for possession of the Brittany ports. At Lorient, Nantes, and St. Nazaire activity was limited to containing the enemy garrisons, and at Morlaix to the protection of the beaches. At St. Malo the enemy stubbornly resisted the siege for two weeks, finally surrendering the citadel on 17 August. In the middle of the month some of the armored units which had spearheaded the race for the Brittany ports began to be released for employment in the Third Army’s eastward drive, and the VIII Corps received in their place some of the First Army infantry divisions pinched out in the closing of the Argentan–Falaise pocket. These divisions were transferred to Brest, where the attack on the port finally got under way on 25 August.
Except for the Brittany ports the “initial lodgment area,” embracing the entire area between the Seine and Loire rivers, had been cleared by 24 August (D plus 79), virtually completing Operation OVERLORD. In fact, operations had already gone beyond the objectives of OVERLORD in the capture of bridgeheads across the Seine. Plans had contemplated a halt at this barrier. But with enemy forces in France greatly weakened and in flight there appeared to be little reason for adhering to original plans.
To exploit this favorable situation the Supreme Command on 19 August made the decision to continue the pursuit of the disorganized enemy forces at the maximum rate which logistical capabilities would allow. First Army’s initial task after crossing the Seine was to encircle Paris, the intention being to avoid a battle for its possession. An uprising of partisans in the city, combined with reports of grave food shortages, brought a change in plans, however, and on 25 August French and American forces entered the capital to assist in its liberation.
At the same time both First and Third Armies, now comprising nine and six divisions respectively (an additional five divisions were engaged in Brittany and along the Loire), began their drives northeastward beyond the Seine. Continuing its giant strides, the Third Army by 29 August had crossed the Marne and captured Reims and Châlons-sur-Marne. Then, turning eastward, it advanced rapidly to the Meuse, crossing at Verdun, St. Mihiel, and Commercy on 31 August.
North of Paris, where the enemy had larger forces and where his retreat had been more deliberate and orderly, Allied advances were not initially as rapid, although the First Army right flank units (VII Corps) made spectacular gains, reaching Soissons on 29 August and Mont-cornet and Rethel on the last day of the month.
The pursuit of the retreating enemy forces was pressed by the Allied armies in the first days of September, although the
pace of the advance was now noticeably affected by lack of supplies, particularly fuel. On the extreme left the 21 Army Group crossed the Somme and captured Amiens on 31 August. Three days later British forces entered Brussels and on 4 September captured Antwerp, with its port facilities for the most part intact. The enemy clung tenaciously to Le Havre until 12 September and then surrendered a badly damaged port. By mid-September British forces stood at the Dutch border.
First Army continued its drive northeastward until Mons was captured on 3 September, and then reoriented its attacks directly eastward. Two days later First Army units crossed the Meuse, and on 11 September made the first penetrations of the German border. By 12 September almost all of Luxembourg was cleared, and with the exception of the left flank the entire First Army now held a line generally along the German border.
Farther south the Third Army continued to press eastward, and on 7 September established the first bridgehead over the Moselle near Metz. In the next few days it made additional crossings near Metz and in the vicinity of Nancy.
Stiffening enemy resistance characterized the fighting of all the Allied armies in the second week of September, and the momentum of the pursuit was abruptly reduced. By 12 September it was apparent that the sustained drive which had begun early in August had come to an end. In the north the enemy now faced the First Army from the formidable defenses of the Siegfried Line; farther south, increasingly favored by the terrain, the enemy fought desperately to halt the Third Army advances at the barrier of the Moselle, launching many counterattacks. In the entire area of the 12th Army Group the enemy had succeeded in stabilizing the front after a near-disastrous rout in northern France.
The VIII Corps continued to engage the enemy in Brittany. On 5 September Third Army was relieved of further responsibility for operations in that area and for security along the Loire, the VIII Corps now coming under the direction of the newly arrived Ninth U.S. Army, commanded by Lt. Gen. William H. Simpson. Fully appreciating the value which the Allies attached to the ports, the enemy successfully resisted the attacks on the Brest fortress for almost four weeks. When the siege finally came to an end on 18 September (D plus 104) he surrendered a thoroughly shattered port.
Meanwhile in southern France Allied forces struck still another blow in an operation subsidiary to OVERLORD. On 15 August the Seventh U.S. Army, with French forces attached, under the command of Lt. Gen. Alexander M. Patch, launched Operation DRAGOON, assaulting the Mediterranean coast of France between Cannes and Toulon. In co-ordination with an airborne drop by British and American paratroops the assaulting forces quickly won a beachhead. Striking both westward and northward, Allied forces captured. Marseille on 28 August and by the end of the month closed in on Lyon, more than 200 miles up the Rhône valley. Matching the lightning sweeps of the 12th Army Group in northern France, the Seventh Army advanced more than 300 miles by 10 September, when it captured Dijon. On the following day armored reconnaissance elements operating west of that city made the first contact with forces of the 12th Army Group when they met a patrol from an armored unit of the Third Army, and within the next few days a
link-up between the two armies was made in force. By mid-September, therefore, virtually all of France, Belgium, and Luxembourg had been cleared of the enemy, and a continuous front from the North Sea to Switzerland had been established.
The Logistic Implications of Changing Plans
In their pursuit of enemy forces across northern France and Belgium the Allied armies began to feel the full impact of logistic limitations. The detailed description of the supply problems of August and early September is reserved for the next chapter. To understand the basic causes for the difficulties and to appreciate the magnitude of the logistic feat of this period, it is helpful to recapitulate the forecasts and estimates of capabilities made by the OVERLORD planners in the months before the actual pursuit.
The OVERLORD plan had contemplated a more or less steady rate of progress which would have taken the U.S. forces to the line Avranches—Mortain by D plus 20, would have uncovered an area southward to the Loire and extending from Lorient to Le Mans by D plus 40, and would have completed the capture of the OVERLORD lodgment area by D plus 90. There was some skepticism concerning the possibility of supporting the operation on the desired scales, but it was generally held before D Day and throughout June that the operation was logistically feasible provided certain conditions were met, in particular that the operation should not proceed faster than scheduled and that the build-up be limited to the size then planned.1
While the plan had regarded the capture of Brittany as a prerequisite to the proper support of operations eastward, the Allied planning staffs in May and June had considered alternate schemes of maneuver which might be implemented should a weakening of the enemy to the south and east permit a drive on the Seine ports in place of the expected advance into Brittany. In LUCKY STRIKE an exploitation was proposed taking the form of a drive toward the Seine with maximum forces in an effort to defeat enemy forces west of the river, followed by a forcing of the Seine and capture of Le Havre and Rouen.2
The reaction to both LUCKY STRIKE and the earlier plan known as AXEHEAD had been lukewarm, mainly for logistic reasons. Granting the desirability of such an operation, the SHAEF planning staff was not very optimistic over logistical capabilities. It estimated that a highly mobile force of only six divisions could take part in the exploitation. Three divisions would be left in the vicinity of Le Mans to protect the flank, and an additional six operating at reduced scales of maintenance and a smaller allocation of motor transport would open St. Malo and continue operations in Brittany. Even this plan would require that the exploiting force be given first priority on supplies, and-movements of reserves to support the forces in Brittany would have to be virtually suspended.
Exploitation across the Seine would obviously be desirable, but it was almost completely ruled out so far as U.S. forces
were concerned. The staff believed that it would be logistically infeasible to maintain anything but the smallest American forces east of the Seine until the lines of communications were organized and stocks built up in forward areas. British and Canadian forces would be in a much better position to seize bridgeheads east of the river, but it was concluded that the participation of U.S. forces should be limited to protection of the British right flank in such operations. British and Canadian forces might in fact be able to launch an armored thrust to the Seine before U.S. forces were ready to participate, and the planners concluded that if enemy resistance weakened sufficiently to permit this, or if the enemy began to withdraw before U.S. forces could be ready, it would actually be unnecessary for American forces to participate even in the advance to the Seine. U.S. participation in LUCKY STRIKE, it was noted, would interfere with the rate of development of an adequate base and line of communications. It would therefore actually entail an administrative handicap which, it was vaguely hinted, might have serious consequences later. The prime consideration was that such an operation must not unduly interfere with the early capture of the Brittany ports.3
While the possibility of assigning a higher priority to the eastward drive and the capture of the Seine ports thus continued to be examined just before and after D Day, there was no alteration in the basic assumption that the possession of the Brittany ports was a prerequisite to sustained operations eastward. During July this concept became even more hardened as a result of the painfully slow tactical progress and in view of the predicted deficiencies in port capacity.
At the start of the COBRA operation on 25 July the front lines were approximately forty days behind the phase lines forecast in plans. At that time the Movements and Transportation Branch of G-4, SHAEF, again analyzed the possibility of supporting U.S. forces at the Seine, assuming that they could still complete the capture of the lodgment area by D plus 90 as originally planned. Since this would require an advance from the D-plus-15 to the D-plus-90 phase line in only forty-one days (from D plus 49 to D plus 90), a considerable acceleration was required. Movements and Transportation officers concluded that in such an advance U.S. forces would be certain to experience supply difficulties by the time they reached the D-plus-80 phase line, for they predicted a shortage of about twenty-nine truck companies. This difficulty might be overcome if an intensive effort was made immediately to move U.S. reserves well forward to temporary dumps in the vicinity of St. Lô. The accumulation of a large stock of supplies in that area would reduce the length of haul later when transportation resources were fully extended. The only other alternatives were to borrow trucks from the British or carry out additional rail reconstruction. At the D-plus-90 phase line (the Seine) the planners estimated that there would be a shortage of 127 truck companies, which could be compensated for only by additional rail reconstruction.4 At the end of
July, therefore, it was estimated that transportation facilities would probably be inadequate to supply U.S. forces even on the D-plus-90 phase line at D plus 90.5 This was indeed a pessimistic view of logistic capabilities.
When U.S. forces suddenly lunged forward at the beginning of August the speed of their advance almost immediately upset all the calculations of the staffs, and brought the planners face to face with the problem they so recently had been debating. On 3 August, with Third Army forces streaming through the Avranches corridor and fanning out to the south and west, General Bradley made a major alteration in the tactical plan when he directed the Third Army to make its main effort eastward, leaving only the minimum forces necessary for operations in Brittany. The importance of Brittany was by no means minimized by this decision; the rapid occupation of the peninsula, in the Supreme Commander’s view, remained a primary task.6 While the redirection of the Third Army’s effort was expected to delay the capture of the Brittany ports somewhat, such a delay was expected to be a minor one and therefore acceptable. Nevertheless this decision marked the first step in a repeated subordination of logistic considerations to prospects of immediate tactical advantage.
During the next few days the easy successes of the Third Army opened up even greater possibilities. The sequence of events and circumstances which developed in the first week of August was remarkably like that upon which the LUCKY STRIKE plan was premised—namely, an open flank had been created in the absence of appreciable enemy forces either in Brittany or in the region of the Loire. These conditions offered the prospect of delivering a decisive blow to the enemy west of the Seine, and the decision was now made to execute the enveloping maneuver already described. On 14 August, after reaching Argentan, the Third Army was ordered to continue eastward, and a few days later its mission was still further extended to the seizure of bridgeheads across the Seine.
Supply planners had been quick to realize the administrative implications of pursuit operations. As early as 2 August, a day after the break-through, Colonel Whipple, chief of the Logistical Plans Branch, G-4, SHAEF, noted that logistic limitations would shortly assume major importance. Anticipating the questions of the operational planners, his group immediately began a study to determine the maximum rate of exploitation which might be supported eastward concurrent with operations in Brittany, and the logistic implications of an early drive to capture Paris.7 Providing answers to these questions involved a thorough review of such factors as port capacities, scales of maintenance, and transportation resources.
By 11 August the G-4 Plans Branch had completed a tentative survey. At that date its estimate of logistic capabilities continued to be guarded. It concluded that four U.S. divisions could be supported in an exploitation to the Seine by 20 August (D plus 75) on the condition that U.S. forces in Brittany were maintained
entirely through Brittany ports or beaches by that date. Those four divisions could participate in a crossing of the Seine by 7 September if four British truck companies, currently on loan to U.S. forces, remained attached until that time, if British engineers assisted in rail reconstruction, and if all rail transport was allocated to U.S. forces. The construction of a 6-inch POL pipeline would have to be speeded and completed to Dreux by 30 August. If, in addition, an average of 1,000 tons of supplies could be made available by air in an advanced area from 20 to 30 August, and again after 7 September,8 it was estimated that the attack across the Seine could be carried out three days earlier and with six U.S. divisions instead of four. Even these estimates were made with caution, for it was noted that there were various uncertainties owing to lack of information and possible variations in the tactical plan. For example, an early capture of Paris would impose an added burden because of the necessity of providing civil relief supplies, and would severely handicap a general offensive. The G-4 Plans Branch recognized that U.S. forces had by far the most difficult supply problem because of the greater distances involved, and would require assistance if they were to participate in the offensive in strength. Rehabilitation of the railways was expected to prove a major factor affecting the speed of the advance, and the most rigid economy in the use of all transportation resources would be necessary.9
In view of the developments of the next few days it would appear that logistical planners had certainly not overestimated the Allies’ administrative potential. Tactical developments took place so rapidly during the time in which the above study was being considered that the premises on which it was based were invalidated by the time it was completed. Within two weeks the advance to the Seine was an accomplished fact, and it had been carried out with a total of seven divisions instead of four.
With the clearance of the left bank of the Seine on 24 August (D plus 79) Operation OVERLORD was virtually completed, eleven days earlier than planned. The decision to drive rapidly eastward following the Avranches breakout instead of employing large forces in Brittany as originally planned resulted in a major tactical victory. But it had already involved at least a temporary subordination of logistic factors, and the difficulties over supply which the armies began to experience as they crossed the Seine foreshadowed serious complications later.
That the lodgment area was cleared eleven days earlier than planned was in itself no measure of the difficulties caused by the rapid advance. More significant was the explosive manner in which the lodgment had expanded following a seven-week confinement in the cramped beachhead. In thirty days (D plus 49 to 79) an area had been uncovered which by plan was expected to require seventy-five (D plus 15 to 90). While the combat forces could easily accelerate their advance, there were definite limitations to the speed with which the lines of communications could be developed. By 25 August U.S. forces were beginning to feel the full effect of the sudden extension of the lines of communications, and the forewarnings which the SHAEF planning staff had made
regarding the effect of U.S. participation in an early drive eastward on the development of a firm base and lines of communications already appeared to be coming true.
But the Allied armies were not to stop at the Seine, and the supply lines were destined to be stretched even farther and faster. In mid-August it was decided to continue the pursuit across the Seine—a decision which was to have considerably more far-reaching effects than that of 3 August. Plans had originally contemplated a pause of at least a month at the Seine, so that an adequate administrative organization could be developed to support further operations. The Allies had never intended to carry on a sustained drive into Germany, nor had they envisaged a decisive battle west of the Seine. Operation OVERLORD had been planned as a preparatory stage, its objective being the capture of a lodgment from which further operations could be carried out. The planning of the entire operation had been dominated by logistic considerations such as the capture of ports, the construction of pipelines, and the rehabilitation of railways. While the Allies hardly expected to capture the lodgment area ahead of schedule, particularly in view of the early delays, much less did they expect to support a drive beyond the Seine before D plus 90.
Planning for operations beyond the Seine (referred to as post-OVERLORD planning) had been initiated before D Day, and the broad course of action in the post-OVERLORD period had been determined by the time the invasion was launched. With the Ruhr, the industrial heart of Germany, as the primary objective, the Allies had decided to make the advance into Germany along two routes. The main effort with the bulk of the Allied forces was to be made along the axis Amiens–Maubeuge–Liége–the Ruhr, and a subsidiary effort with smaller forces on the line Verdun–Metz–Saarbrücken.
As usual, logistic factors figured prominently in determining this course of action. The two-pronged advance had initially been ruled out because of the disadvantage of maintaining forces on two widely separated lines of communications. It had finally been adopted in the belief that success along one axis would force enemy withdrawals in both areas, leaving adequate lateral communications between the two axes.
The requirement for ports was also a major determinant, since the capacity of those in the OVERLORD lodgment area was believed to be inadequate to build up and maintain forces required for the final defeat of Germany. The acquisition of additional port capacity before the onset of autumn gales was particularly essential to the support of British forces since the usefulness of the beaches and MULBERRY, on which they were initially dependent, was certain to come to an end in September. Logistical requirements therefore pointed to the earliest possible seizure of the ports of Le Havre and Rouen. Even with these, however, it was estimated that the available capacity would continue to limit the forces which could be maintained, and it was believed necessary to seize the Channel ports as far east as Antwerp to ensure satisfactory maintenance of the Allied forces. These considerations consequently supported the argument for a major effort northeastward paralleling the Channel coast.10
In outlining the course of action to follow the capture of the lodgment the planners had concluded, furthermore, that logistic difficulties precluded the mounting of an offensive south of Paris at an early date. For a long time U.S. forces would have very extended lines of communications, based in part on Cherbourg and the Brittany ports even after Le Havre was transferred to American use. Delays in the reconstruction of damaged rail lines were expected to limit the rate of advance for some time after the initial crossing of the Seine. Consequently the possibilities were considered best for mounting an offensive first across the lower Seine, between Paris and Le Havre.11 Because of the handicap under which the U.S. forces would be operating, it was held that they would probably be unable to make their main thrust from the lodgment area before D plus 120, when the U.S. advance base would be firmly established in the Rennes–Laval area, with subsidiary depot areas in the vicinity of Chartres and Le Mans in addition to those in the Cotentin.12 British forces were expected to be able to renew the offensive about one month earlier.
Allied planners continued to examine the various possibilities for launching an offensive from the lodgment in the weeks following the launching of the cross-Channel operation. In the middle of June they momentarily gave thought to a proposal to force an early battle west of the Seine and exploit across the river without waiting for the development of the longer U.S. lines of communications. This plan called for a concentration of the major Allied effort west of the lower Seine and a crossing of the river below Paris. Maintenance of both British and American forces under this plan would be effected mainly along the British supply routes.13
The planners had not changed their views appreciably by early August. At that time they still estimated that, because of transportation deficiencies on the long U.S. lines of communications a maximum of not more than four U.S. corps could be supported as far east as the Seine–Mantes–Loire line. Any advance beyond that line before October could be achieved only by reducing the road transportation commitment of other U.S. forces to the minimum by stationing resting divisions near depots and ports, by limiting the expansion of the American right flank to the southeast, and by utilizing airborne maintenance. Even then it was thought that only two U.S. corps could be maintained in an assault north or south of Paris in September. Furthermore, the capture of Paris before late October would mean burdening transportation with additional commitments for civil affairs supplies (food, coal, medical supplies) and would thus impose a severe limitation on the maintenance of operating divisions. For this reason it was desirable to postpone the capture of Paris until rail facilities could be developed from the ports in Brittany and Normandy and until the Seine ports were captured. From the above factors the planners concluded that any advance in strength east of the Seine–Mantes–Loire line before October would have to be conducted mainly by British forces and would have to be made along the lower Seine, between the Oise and Rouen. In fact, in view of the urgency of opening the Seine ports they thought that it might be necessary to employ one to three U.S. corps
north of the Oise if delays in operations were to be avoided.14
Toward the end of the month, with Third Army units already across the Seine at Mantes-Gassicourt and preparing for additional crossings above Paris, the planners began to consider bolder actions than they had thought possible a few days before. On 22 August they analyzed the capabilities of supporting a drive across the Seine near Mantes to seize Amiens and Abbeville, employing thirteen U.S. divisions in the main effort and thirteen British divisions in a secondary attack. Such an operation they regarded as feasible, but only by ruthlessly subordinating all considerations other than the support of the main effort. The attack would have to be launched with less than the normal scale of reserves; maintenance in army areas was to be partly at normal rates (535 tons per division including POL) and partly at reduced rates (407 tons); the rail system would have to be reserved for U.S. support; two U.S. divisions were assumed to be immobilized in the Brittany peninsula, and were to give up their organic truck companies plus improvised companies; and a loan of forty-nine British truck companies was assumed. Deficiencies in rail transportation, which was expected to reach Dreux and Chartres by 1 September, were expected to be met by air supply or by temporarily pushing trucking units beyond their rated capacities.15
On the following day G-4 officers at Supreme Headquarters, envisaging more ambitious plans for a rapid advance beyond the Seine, issued an estimate of the special measures which would be necessary to insure the maintenance of forces engaged in such an advance. Even at that date, however, it was inconceivable to the administrative planners that sufficient support could be provided to maintain the advance on the scale and at the speed of the past few weeks and carry the Allied armies to the German border. They assumed, for example, that only eleven U.S. divisions (four armored and seven infantry) could take part in a continued drive, all others remaining in defensive positions along the Loire or in Brittany, or entirely static in the Alençon–Le Mans area. Scales of maintenance would have to be drastically reduced for even the eleven divisions participating—to 162 tons per day for infantry divisions and 247 tons for armored divisions fully engaged, and 108 and 141 tons per day respectively for divisions not fully engaged. Advancing divisions, furthermore, were to take with them none of their heavy artillery and only 50 percent of their medium artillery, and ammunition expenditures were to be limited to one third of the normal expenditures of divisions in the line. Reserves were to be reduced to half of normal, and accumulated only for divisions actively engaging in the advance.
On these “iron rations” and through various expedients, such as the organization of provisional truck units from inactive divisions, the planners thought that the advance could be continued and supported by road and rail. Should actual requirements prove heavier than those estimated, especially in ammunition and in engineer and civil affairs supplies, maintenance by air would definitely be necessary. The margin was therefore admittedly closely drawn, and support of the operation was made additionally precarious by serious shortages of service
units, particularly ordnance depot companies and heavy truck maintenance companies, engineer truck companies and maintenance companies, and quartermaster truck units. With the above scales of support the planners foresaw an advance only to the Somme River and slightly beyond Laon, Chalons-sur-Marne, and Troyes by 20 September, and just beyond Sedan, Metz, Nancy, and Chaumont by 20 October.16
In the midst of these calculations the Supreme Command decided that Allied forces would cross the Seine without pause, and subsequently extended the objectives of the armies farther and farther eastward. Furthermore, the earlier plan providing for a secondary effort along the Reims–Verdun-Metz axis by only a small force was now expanded to provide for an advance in considerably greater strength along the subsidiary axis. Early in September the Third Army was directed to continue eastward with the mission of occupying that portion of the Siegfried Line covering the Saar, and then crossing the Rhine to capture Frankfurt.
A comparison of the administrative appreciations of this period with the actual course of operations presents sharp contrasts. The progress of the Allied armies in the six weeks following the breakout on 1 August appears to have invalidated the conservative estimate of logistic capabilities. Ignoring even the most optimistic estimates of what was possible, the armies by D plus 98 (12 September) advanced to the line which the forecasts had indicated they would reach on approximately D plus 350.
Between 25 August and 12 September they had advanced from the D plus 90 to the D plus 350 phase line, thus covering 260 phase-line days in 19 days. The record was actually more phenomenal than these figures indicate, because in the earlier dash to the Seine the armies had overcome an initial lag of 30 days. Moreover, Paris had become an additional supply liability as the result of its liberation 55 days ahead of schedule, and whereas it had been estimated that only 12 U.S. divisions could be supported as far east as the Mantes–Orléans line at D plus 90, 16 divisions were being maintained in the vicinity of the Seine at D plus 79, and an additional 5 divisions in Brittany. In mid-September 16 U.S. divisions were being maintained 200 miles beyond the Seine, albeit inadequately, plus several divisions on combat scales in Brittany. By unusual exertions this feat was accomplished despite the fact that few of the conditions laid down in administrative estimates, such as the maintenance of Brittany forces via the Brittany ports and beaches, or extension of POL pipelines to Dreux, were met.
Supporting the advance to the German border and the Moselle by mid-September in a gamble for a quick victory entailed a ruthless disregard for an orderly development of the communications zone. The cost at which this overexertion was made was to be fully revealed in succeeding months.