What was the size of the us military before and after World War 2?

Answer 1

The US Army had around 200,000 officers and men in the mid to late 1930s, and was the 21st largest in the world (right behind Bulgaria). In 1945 there were more than 8 million men in the Army, so it was more than 40 times larger than during the Great Depression.

The Air Force was still a part of the US Army, as the Army Air Corps (changed to the US Army Air Force in 1940 or 41). It was tiny, with no airplanes which would be able to serve effectively in the war. The design of the B-17 bomber was made in 1935, but the early versions were nowhere near as robust as the design became, after five design evolutions. It was the B-17E which first saw service in Europe, and the F and G models were even better, and more than 12,000 were made. This was the airplane most closely associated with the bombing of Europe from England by the US 8th AF. There were actually more B-24s in that effort - there were 18,000 B-24s made, but it had not even been designed in its first version yet, and neither had the B-29s which bombed Japan, nor any of the fighter planes which protected them and killed the enemy air forces - the P-47 and P-51. By the end of the war more than three million men served in the Air Force, which had tens of thousands of airplanes. (And remember, these three million and the more than eight million in the Army Ground Forces were all under the command of George Marshall, who was the true architect of victory, but is remembered more today for his Marshall Plan. Marshall had always intended to go in person when the invasion of Europe was made, and lead the US Army he created to victory, but President Roosevelt said he would not be able to sleep at night if Marshall was away from Washington, so Marshall was forced to stay, and to appoint his protege Eisenhower to the command in his stead. As a result, Eisenhower got to be president, and Marshall is not much remembered today.)

Roosevelt had been Assistant Secretary of the Navy during WWI, and took great interest in the Navy. Like the other services the Navy was strangled for money between the wars. It takes a long time to build a big ship - years. The Navy began designing the new generation of battleships in 1935, but the first one was not finished until 1941, and it was the first new US battleship in more than twenty years. Eventually there would be ten of these new "fast battleships", to go with the 15 old slow ones left over from WWI. There would be dozens of new heavy and light cruisers, and hundreds of new destroyers, a total of more than one thousand warships, plus many thousands of auxiliary types. Aircraft carriers turned out to be the crucial type of warship, especially for the Pacific. When the war began the US had six large "fleet carriers", plus one small one built as an experiment. By the end of the war the US had more than two dozen fleet carriers, and another several dozen light carriers, and scores of escort carriers, made by converting a merchant ship design, used to escort ship convoys and protect them from submarines. The US built many dozen fleet submarines, for long range war patrols, again mostly in the Pacific. Submarine sailors made up 1% of the US Navy, but sank 55% of all Japanese ships sunk by the US Navy. About three million men were in the US Navy during the war.

In all, more than 16 million Americans were in uniform during the war. This was 10% of the entire US population of 160 million.