US Army strength Sept 1939

[Sequoia]

I've looked for this online with no success. Can any one tell me or give a link to the size of the US Army in divisions and independent brigades at the start of WWII?

Thanks in advance.

[JasonC]

Here is a capsule history of US army strength between the wars, and the build up after war broke out in Europe (especially after the fall of France) but before Pearl Harbor.

The US demobilized rapidly after WW I. Brass wanted a large peacetime force of half a million men and a regular rotating reserve, along the lines of European continental powers. But congress was having none of it, and by 1922 the army shrank to 10,000 officers and 125,000 enlisted, (active) a strength it remained at through 1936. The entire war department budget was $300 million, half the amount required to maintain the authorized force, and the navy took the lion's share of that budget.

The army had 9 infantry divisions on strength at that point, but the manpower only kept them at about 1/3rd of TOE strength. The units deployed in the Philippines, Hawaii, and Panama were somewhat nearly authorized strength, the stateside ones less so. All that is the active army. There was also the National Guard, with 180,000 reservists training regularly. An additional manpower pool was the ORC (officer's reserve), initially consisting of WW I veteran officers who kept their commissions but returned to civilian life, and later filled with ROTC program graduates who did not join the service on graduation. In all there were thus 400,000 men available to be called on, some as cadre and some as immediate defensive manpower during a mobilization period. The army planned to expand to 1, 2, or 4 million men in wartime from this base, depending on events (of course it exceed the highest figure in the real deal).

There was no uptick in this until after 1936. There was then a very modest expansion of the active army to 165,000 men, and the budget was expanded enough to update equipment for some and develop prototypes etc. At that point over 30% of the active army were in the coastal defense artillery, to give you an idea.

On the outbreak of war in Europe, the active army was authorized to expand to 227,000 men and the National Guard to 235,000. The navy was in a major building program. But there was not yet any serious mobilization and budgeting remained tight. That changed overnight when France fell. Before then, strategists had envisioned a need to support the allies economically and perhaps with naval forces, and to be prepared to defend the hemisphere. Japan was also on the threat board. But it was still believed that the main European war would prove long and indecisive, as WW I had, with the French and British carrying the burden. When France fell they panicked and realized they had to mobilize immediately, and would need to create a large land force and send it to Europe before it was over.

So the army doubled in the second half of 1940. The budget jumped to $8 billion for the coming year, which exceeded the defense appropriations of the entire interwar period. The National Guard was federalized, and in 1941 its 1-year active commitments extended to 18 months. The ORC was also called up, and the first peacetime draft in US history authorized. By mid 1941 the army had expanded to 1.5 million on active duty, for a force of 25 infantry divisions, 5 armored divisions, 2 cavalry divisions, and 35 air groups. Of course, most of these were still training and they were not yet ready for serious action. But the active army was 9 times larger than the 1938 level by mid 1941, having called on all its existing reserves and a million men more besides.

So, 1938 or 9, nothing much, just cadres, overseas garrisons, and coastal defense. Summer 1940 after France falls, jumping through their behinds, and as a result by the summer of 1941, 32 divisions and 35 air groups on strength, readiness and weaponry all expanding. The mobilization accelerates after Pearl Harbor of course, but it began 18 months earlier at the fall of France.

I hope this helps.

[Sequoia]

Yes, thanks. That is very helpful. What I'm trying to do is a bit of wild speculation. What if the U.S. entered the war in 1939 along with Britain and France. What sort of forces could/would they commit to France by May 1940? Given what you've said and the strong forces that would still be against intervention, I would suppose no more then six infantry divisions and an armored brigade along with air forces probably in line with what the RAF commited to France. Any opinion?

[JasonC]

Forces against intervention have nothing to do with it, it is purely a matter of when they decide to mobilize. Historically that was when France fell, and 12-18 months later they have 25 IDs and 5 ADs training up. There are only 8 months between Poland and France. If they do in September 1939 what historically they did in May 1940, then in May 1940 they wind up where they were historically in February 1941, approximately. Which is "not ready for much of anything", and that only stateside. To actually deploy forces to Europe takes months, on top of month of mobilization time and training time. They just don't get there, with anything.

The first serious commitment is North Africa for Torch, and it is only 2 ADs and 3 IDs from the US in the first wave, 18 months after mobilization. Half that prep time, no way you get 6 divisions and change out at the pointy end. You'd have that or more stateside but still in training.

[Sequoia]

So for there to be any realistic chance of having any significant forces in France in May 1940 the U.S. would have had to have undergone a prewar rearmament and mobilisation much as the British had done in the late 1930's.

[JasonC]

They would have had to fund the peacetime army from about 1938 or so, and call up the National Guard and officers reserve corps at the outbreak of the war. That might get a force of half a million under the colors by May 1940. It wouldn't put even half of that in France. The highest readiness divisions would be in Manila, Hawaii, and Panama even in that event. There might be 10 deployable divisions in the whole force, and half of them would be spoken for by the Pacific or necessary stateside reserve. An "AEF" would be corps sized even with a 1938 budget and immediate reserve mobilization.

The Romanian army was vastly bigger and readier than the US army was. The Poles and the Czechs have much more to offer in aid to France, at the relevant time scale. The US would matter if France held so that it became a long attrition war, however. It might in that event put a dozen divisions into France in the course of 1941, and a useful air arm by a similar date. But they won't get there full dress in May of 1940.

That was written into the cards by the post WW I drawdown to a barely existent active duty army, by funding mostly the navy in the interwar years, and by keeping only a small volunteer reserve as a cadre for wartime mobilization, not as a standing peacetime mobilization-ready force on the European continental pattern. The brass proposed that in 1918 but it was nixed by congress. It is extremely doubftul that funding for such a thing would have held up through the depression even had it been in place, come to that. But doubtless the reserves would have been much much larger, even if the bigger peacetime idea had a transient existence 1918 to 1933, say.

It turned out not to be necessary to have such a big ready reserve, to achieve a huge mobilization and fully deployable combat power. But not having one did mean a 2 year warm up time was baked in. The reason all the combatants in WW I and the continental powers in WW II can conjure million man armies out of the ground at the drop of a hat, is they were all inducting regular classes into large peacetime armies, and then cycling those trained men into their huge reserves, continually. This always left them with a large training cadre, a large active force at high readiness for immediate use, and the ability to expand that force 3 to 10 fold on a time scale of weeks. Only a peacetime draft gives you that mobilization ability.