The process of mobilization for this war reached its peak and immediately started to decline with the surrender of Germany. In the summer of 1943 the firm decision was reached to build up the Army to an effective strength of 7,700,000 enlisted men believed necessary to meet our strategic commitments.
At the close of the European war the operating strength of the Army plus ineffectives was approximately 8,300,000. The ineffectives consisted of 500,000 men undergoing hospitalization, including 100,000 in the process of being discharged because they were no longer fit for either active or limited service, and 100,000 en route overseas as replacements, in all totaling approximately 600,000 men. . . .
The technique for the mobilization of American manpower in this war was unique. The special nature of the war introduced many new factors. Perhaps greater than any other single advantage of the United Nations was the productive capacity of American industry. It was therefore necessary not to cut too deeply into the manpower of the Nation in the process of acquiring the men urgently needed by the Army and the Navy. We had the problems of arming both ourselves and the Allied Nations while, at the same time, we created huge armed forces necessary to the successful prosecution of the war. Furthermore, our lines of communication were to be extended entirely around the world, requiring large forces of men to work them and absorbing even larger forces in transit over the thousands of miles to and fro without profit to the military enterprise.
Fighting across the oceans, we needed a very powerful Navy and a large merchant fleet to transport and maintain our armies and to carry munitions to our Allies. At the same time, it was our purpose to exploit every possible scientific device and technique to secure victory at the smallest cost in lives of our men. These various efforts demanded large numbers of men and women, and necessitated their allocation among the various programs with exceeding care, so that the right numbers of men would be doing the most important things at the most important time. The mere statement of this requirement fails to indicate the exceeding difficulty involved in its application to the special claims of each industry and the demands of each theater commander. To resolve the conflicting requirements posed a most difficult problem for a democracy at war.
It was estimated that the absolute ceiling on the number of American men physically fit for active war service lay between 15 and 16 million. The requirements of the naval and merchant shipping program had to be given a high order of priority. The Army decided to establish its strength ceiling at 7,700,000. Before we could bring the enemy to battle we had to secure our lines of communication and build our training and service installations. Within this total strength of the Army the minimum requirements of the Service Forces were set at 1,751,000. It was decided at the outset that the first offensive blows we could deliver upon the enemy would be through the air, and anticipated that the heavier and more effective our air assault, the sooner the enemy's capacity to resist would be destroyed. So the Air Forces were authorized to bring their strength to 2,340,000 men and were given the highest priority for the best qualified both physically and by educational and technical ability of the military manpower pool.
Each theater of operations had requirements for men over and above those allocated for its armies, air forces, and service installations. The troop basis allowed 423,000 men for these troops which would be directly attached to theater headquarters and major command installations throughout the world.
This left the Ground Forces with a maximum of 3,186,000 men within the limitations of the 7,700,000 effective troops strength. Yet when we entered the war it was almost impossible to compute accurately how many ground combat troops we would need to win. The precise results to be attained by modern aerial warfare could only be an educated guess.
. . . [I]n early 1942 we established a troop basis of 3,600,000 men which would permit the organization of 71 divisions: 59 infantry (including 18 National Guard), 10 armored, and two cavalry. This force was the largest we then had the ability to train, equip, and provide a nucleus of trained officers and noncommissioned officers. In mid-1942, when the original build-up in the United Kingdom for the invasion of France and the North African operation began to take shape, we found we needed more and still more service troops. The demand was insatiable. The over-all strength of the Army by the end of the year had increased to 5,397,675 men. Throughout 1942, however, the planners were at work estimating the requirements for 1943 which we believed would carry the Army to its peak of mobilization and would give us the necessary strength to force a victorious decision. At first it was estimated this would provide the Army with 105 divisions. Later it became evident that the men for only 100 divisions could be found with this strength. By the middle of 1943 we determined that this projected mobilization might impose too great a strain on the Nation's manpower, if all of the ambitious efforts planned for the global war were to remain in balance. Fortunately for our dilemma, Stalingrad was now past history and the great Soviet armies were showing a steadily increasing offensive power. The ceiling was therefore reduced to 7,700,000 shortly after the TRIDENT Conference in Washington, the meeting at which the over-all strategy became sufficiently firm to permit more precise planning. This amounted to a reduction of 548,000 men. The projected number of divisions was reduced to 90, including three special or "light" divisions that were being trained for jungle and mountain warfare. Later the 2d Cavalry Division, then in North Africa, was activated to provide urgently required service troops to support the amphibious landing in southern France. At the same time the Air Force mobilization was fixed at 273 combat groups containing five very heavy bombardment (B-29s and 32s), 96 heavy bombardment (Flying Fortresses and Liberators), 26 medium bombardment, 8 light bombardment, 87 fighter, 27 troop carrier, and 24 reconnaissance groups.
On the face of it this appeared to be a critically small ground force for a nation as large as ours. Germany with a prewar population of 80,000,000 was mobilizing 313 divisions. Japan was putting 120 in the field; Italy 70; Hungary 23; Rumania 17; Bulgaria 18. Among the major Allies, the Soviets had a program for more than 550 divisions; the British for more than 50; the Chinese more than 300, though their divisional strength was often little more than regimental according to our method of computation. We were, however, second of the Allies in the mobilization of men and women for military service, third among all the belligerent nations. The Soviet war effort was putting 22,000,000 men and women into the fight. By the time of their defeat, the Germans had mobilized 17,000,000. Our peak mobilization for the military services was 14,000,000. The British Empire mobilized 12,000,000; China 6,000,000.
This war brought an estimated total of 93,000,000 men and women of the Axis and United Nations into the conflict. And fortunately for us the great weight of numbers was on the side of the United Nations. Total Allied mobilization exceeded 62,000,000; total enemy mobilization, 30,000,000. The figures show how heavily the United States was concentrating on aerial warfare, on the production and movement of arms for its own troops and those of its Allies, and the meaning in terms of manpower of waging war from 3,000 to 9,000 miles from our shores.
Our ground strength was, for the size of our population, proportionately much smaller than that of the other belligerents. On the other hand it was, in effect, greater than a simple comparison of figures would indicate, for we had set up a system of training individual replacements that would maintain 89 divisions of ground troops and 273 combat air groups at full effective strength, enabling these units to continue in combat for protracted periods. In past wars it had been the accepted practice to organize as many divisions as manpower resources would permit, fight those divisions until casualties had reduced them to bare skeletons, then withdraw them from the line and rebuild them in a rear area. In 1918 the AEF was forced to reduce the strength of divisions and finally to disband newly arrived divisions in France in order to maintain the already limited strength of those engaged in battle. The system we adopted for this war involved a flow of individual replacements from training centers to the divisions so they would be constantly at full strength. The Air Forces established a similar flow to replace combat casualties and possible relief crews.
This system enabled us to pursue tremendous naval and shipping programs, the air bombardment programs and unprecedented, almost unbelievable, production and supply programs, and at the same time to gather the strength necessary to deliver the knock-out blows on the ground. There were other advantages. The more divisions an Army commander has under his control, the more supporting troops he must maintain and the greater are his traffic and supply problems. If his divisions are fewer in number but maintained at full strength, the power for attack continues while the logistical problems are greatly simplified. . . .
The final manpower crisis occurred during the prolonged and very heavy fighting in the fall of 1944 and the winter of 1944–45, both in Europe and in the Philippines. However, our own tribulations of this nature were much less serious, it is believed, than those of our Allies and certainly of the German enemy, whose divisions at times were reduced below 5,000.
In the Siegfried Line fighting prior to the final advance to the Rhine, the weather was atrocious and most of the troops had been continuously engaged since the landing in Normandy in June. The lack of port facilities prior to the opening of Antwerp to Allied shipping made it impossible to maintain divisions in normal corps reserve and thus permit the rotation of units between the fighting line and comfortable billets in rear areas. Divisions for this purpose were available in England and in northwestern France, but the state of the railroads and the flow of supplies made it impossible to maintain them at the front. All this resulted in a great strain on the fighting troops, and when a shortage in replacements was added, the situation great very serious. It was just at this moment that the Germans launched their final offensive effort in the Ardennes. . . .
To implement the replacement system we had established the Ground and Service Force Replacement Training Centers. It required more than a year to train the many elements of a new division because of the difficulties of teaching men and units the teamwork so essential under the trying conditions of battle. But it was possible and practicable in a much shorter time to train an individual soldier so that he was competent to join a veteran team as a replacement where the battle experienced soldier can quickly fit him into the divisional structure. At the replacement training centers men were made ready to join the divisions and replace casualties in a concentrated training period of 17 weeks. At these training centers they were given six weeks of basic military training and intense physical conditioning. In the remaining period they acquired competence in handling the weapons with which they would fight or the equipment with which they would work and in learning the tactics of squads, platoons, companies, and battalions, the tactical units which actually engaged in combat.
An infantryman, for example, became proficient in his primary weapons and familiarized with the M1 rifle, the carbine, the hand grenade, the rifle grenade, the automatic rifle, the .30 caliber medium machine gun, the 60-mm mortar, and the two-man rocket launcher. These were the weapons that every infantry rifleman might be called upon to use. Not only were men taught to handle their weapons with proficiency in the replacement training centers, but they were taught to take care of themselves personally. There was intensive instruction in personal sanitation, malaria control, processing of contaminated water, cooking, and keeping dry in the open and all the other lore that a good soldier must understand. But most important, our replacements were taught the tricks of survival in battle. As the Army acquired battle veterans, both officers and enlisted men were returned to the United States for duty as instructors in the replacement training centers. These veterans, who learned how to survive in combat, passed on knowledge to new men and thereby increased both their effectiveness and their chances of survival in their first experience of combat. The training of replacements was made as realistic as possible to manage in training. Problems of street fighting, jungle fighting, and close combat were staged in realistic fashion with live ammunition, and men learned to crawl under supporting live artillery barrages just as they must in battle. Although this training cost us a few casualties in this country, it is certain that for every casualty we took in this manner, we saved the lives of many men in battle.
After the completion of their replacement training, men received a furlough at home before reporting to oversea replacement depots where their long journey to the fighting fronts began. In the theaters of operations they again staged through the replacement depots which were established in the rear of each army group, army, and corps. When division commanders needed new men to replace casualties, they called on corps replacement depots and the men moved forward to the line.
Where it was possible, the replacements were absorbed in the division in its inactive periods, or in regiments in reserve positions, and each new man was teamed up with a veteran so that he could learn to know his squadmates before he saw action. But when the battle was moving at a fast pace, replacements at times had to join units engaged with the enemy.
By the spring of 1944, as most of the shortcomings of the replacement system had become evident, the War Department took vigorous corrective action. A directive was sent to every theater requiring the establishment of retraining centers so that every man in the Army would be put to his most efficient use.
Since the early critical days of the mobilization, the Service Forces, the Ground Force training commands, and particularly the Air Forces had acquired great numbers of the best qualified of our men. The shortage of physically qualified men for infantry and artillery became apparent about midway in the activation of the new divisions. Later we started approaching the bottom of the manpower barrel, and it grew increasingly difficult to get men physically fit for combat out of the remaining civilian manpower pools. The only way in which the battle line could be kept firm was with suitable men already in the Army. To do this we speeded up the training program and stripped the divisions training in this country of nearly 90,000 infantrymen. At this same time the overseas divisions were returning increasing numbers of sick, wounded, and injured men to the hospitals as the intensity of the fighting developed and sickness took its toll. It was our purpose to fill up the service units with these hospitalized men who still could serve their country but no longer could endure the extreme hardships of the fox holes, and to send forward fresh men to take their place, after a necessary period of retraining.
In the United States we resolved to move out all physically fit men from the service and training commands and replace them with men who had been wounded or weakened by disease and the hardships of the front, with men who had been overseas so long that they were entitled to return home under the rotation policy, and where possible with civilians. . . .
To keep the overall effective strength of the Army within the troop basis of 7,700,000, the call on Selective Service had been reduced from 160,000 a month in early 1944 to 60,000 in the fall. But when the replacement crisis reached its peak in the winter, there was no remaining alternative but again to call on Selective Service for more men. The call was increased to 80,000 in February of this year and 100,000 a month thereafter to the end of June. . . .
It is remarkable how exactly the mobilization plan fitted the requirements for victory. When Admiral Doenitz surrendered the German Government, every American division was in the operational theaters. All but two had seen action; one had the mission of securing the vital installations in the Hawaiian Islands; the other was an airborne division in SHAEF Reserve. To give General Eisenhower the impetus for final destruction of the German armies of the west, two divisions, already earmarked for future operations in the Pacific, the 86th and 97th, were halted on the West Coast in February, rushed across the United States and onto fast ships for Europe. When these troops left the New York Port of Embarkation there were no combat divisions remaining in the United States. The formed military forces of the nation were completely committed overseas to bring about our victory in Europe and keep sufficient pressure on Japan so that she could not dig in and stave off final defeat.
The significance of these facts should be carefully considered. Even with two-thirds of the German Army engaged by Russia, it took every man the Nation saw fit to mobilize to do our part of the job in Europe and at the same time keep the Japanese enemy under control in the Pacific. What would have been the result had the Red Army been defeated and the British Islands invaded, we can only guess. The possibility is rather terrifying.
George C. Marshall, General Marshall's Report: The Winning of the War in Europe and the Pacific: Biennial Report of the Chief of Staff of the United States Army July 1, 1943 to June 30, 1945, to the Secretary of War (New York: Simon and Schuster, 1945), 101–107. .