Military hiring and spending is government hiring and spending. I am glad we entered World War II. Nevertheless, if the War had not been going on, and if the government had spent the money instead on infrastructure, public health, public education, and other aspects of public spending, the results would have been better for the economy.
PART THREE:
We've covered the ocean and air transportation systems and infrastructures needed to be built to sustain the USA's global war effort; which then became surplus to the nations of the world for their use and repair/development post war. Now comes a quick consideration of the "boots on the ground" part.
In this case much more than just the USA's ground combat forces of the Army and Marines, but also the supply/logistics that sustained such and also "spilled over" to the Allies and non-combatants involved as well.
In the case of Russia/USSR, much of their food growing regions were combat zones for a few years during the war, with wars raging and fighting across such, very little food was grown and harvested. It was USA food supplies; "wheat and spam" that kept Russia feed and in the war. Actually, USA food supplies kept our other Allies going as well. We were the "Breadbasket of Democracy" as much as the "Arsenal of Democracy".
Also in regard to the USSR, about 90% of their motor transport, trucks and jeeps, also came from the USA. Not only were ours of better quality and duration, but this freed Soviet factors to churn out tanks and combat vehicles since we took care of he bulk of the motor transport needs.
USA~Allied Lend-Lease also provide about 10%+ of combat aircraft, AFVs, and guns/weapons, and a majority of radios and other misc. equipment to the Soviets. Fair to say that at first this kept them from collapsing and loosing, and then helped them to win.
We also provided significant motor transport to the UK and other Allies as well. Most of this was left behind in their hands at war's end to help rebuild/restart their motor transport infrastructure.
The USA also bore the brunt of refugee feeding, clothing, shelter to help the liberated nations get back on their feet. Also a bit of the civic and industrial reconstruction as well.
USA expenses in World War Two weren't just "guns and bullets"; a majority was everyday living needs like food, clothing, shelter, etc. that we were providing in the liberate lands while they made their recovery.
We did a lot more than we ever got credit for, and this late in the game I doubt we ever will get the credit of what we paid for.