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You can break down the U.S. war effort in World War II by the numbers, and most of them are pretty impressive.  Tanks, aircraft, ships, weapons and weapons systems of all sorts:  the “arsenal of democracy” supplied them all in abundance, essentially out-producing the rest of the world both friendly and hostile in the course of the war.  It was this abundance of materiel that allowed the U.S. military to pursue its preferred strategy of applying overwhelming combat power directly against the enemy’s main force and crushing it.

But there was one area where it had consistent problems:  finding enough manpower.  The country had a good-sized population, to be sure, 133 million in 1941, compared to 80 million Germans (1939 population) and Japan (105 million, also in 1939).  But those countries managed to deploy somewhere around 300 divisions and 100 divisions, respectively, in the course of the war.  And as every student of the conflict knows, the U.S. limited itself to just 90 (actually 89, once the 2nd Cavalry Division was inactivated in early 1944).  That was nowhere near the 200 divisions General Lesley McNair estimated the army would need, an estimate he made the day before Pearl Harbor, and farther still from the 334 division army envisioned by the Joint Chiefs of Staff in early 1942.

It is often called a mistake, and indeed, there were times in this war–many times–that U.S. commanders wished they had another division or two to plug into a gap, or to relieve a front line division that was starting to feel the pinch of losses, fatigue, or demoralization.  By late 1944, with gigantic, infantry-heavy campaigns taking place in the Philippines and Western Europe simultaneously, the U.S. Army had been stretched about as far as you could stretch it.

But what were the alternatives?  Take those original impressive population numbers.  Now consider that one of the basic Allied strategies was to have the U.S. serve as the industrial arsenal for the alliance.  That means bodies–lots of them–in the factories.  Then take that war with Japan.  That’s going to require a navy–a big one that was eventually some four million strong.  Now subtract the requirements for the U.S. Army Air Forces (another two million plus).  What does that leave?  Army Ground Forces that, by March 1945, numbered some 2.5 million men.  Subtract support personnel, and you wind up with… somewhere around 89 divisions to do the actual fighting.

It’s not really a mistake if you have no choice.

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