Perhaps its just selection bias, but it has struck me that from a design perspective WW2 in most nations produced iconic aesthetically pleasing designs, like the Zero, Spitfire, Mustang, The Jeep and the Tiger, Garand Rifle, etc.
I wondered what if any sort of artistic movements inspired these sort of aesthetics, was it just happy coincidence or if because of their function in the war that in turn has made the design iconic.
I would not say the Jeep, Tiger, or Garand were ‘aesthetically pleasing’. They were all hyper functional, and flawed (ever sit in the back of an original jeep and go over a bump?); the Garand was nice but not as nice as, say, an MP-38, to my eye. The Tiger was downright ugly, to my eye (especially the Tiger I); a Panther might be a better choice - so long as you can keep the treads on 
But the aircraft, I’d agree; they had to be aerodynamic; clean-lined, and simply shaped. Such shapes are pleasing to the eye, much like porpoises, whales, or sharks. The Spitfire has been called one of the most beautiful aircraft ever built, for instance. (Though not by many Me-109 pilots.)
The only design school I can think of that might have had an influence on WWII designs would be Bauhaus, which praised functional design as integral to its artistic value. But better minds than mine can comment on that…
Pretty or pleasing or not they are in every bit of pictures and movies and photos of WW2 we see so maybe that’s why you think of them as pleasing. I would use the term iconic instead. When we see these pictures we all know what we are looking at.
Although I will say looking at an Iowa class battleship was quite an inspiration. Although the world war 2 configurations of most ships put guns everywhere they could to deal with Kamikazes. I loved Drachinefels comment that every American got to express his second amendment rights 
For planes specifically, I think most of it came from the understanding of aerodynamics. There was also not yet a well-defined optimum or industry standard that every design would be based off, so that’s why you see so many different iconic models. There was also the fact that not all planes were designed for the same role or purpose. The mustang was designed as a long range escort and its design would be influenced by it, while Spitfire’s were designed with more of a home defense/interception plane in mind.
Finally, it’s worth noting that these were subsonic planes, so aerodynamics act very different on these planes compared to modern jet fighters.
Not an original … although the Canadian army in the 70s still had a lot of WW2-era equipment in service. The one I nearly bounced out of was Korean War-vintage.
I don’t think Bauhaus had much impact outside Germany until after the war. The artistic influences of the 1920s and 1930s drew much from the Art Deco movement (disclaimer: one of my favourite styles) and the earlier Art Nouveau of the early 20th century, but was pretty much gone from the scene by the time the rearmament programs got underway. Socialist Realism and it’s less-explicitly-Soviet equivalents were probably the most dominant by that point, but I don’t see much connection with military equipment of the era.
Most WW2 equipment, planes, ships , vehicles and so on were designed for functionality over form. The fact that some of the equipment had pleasing lines and aesthetics most likely was by chance.
The Willies Jeep was not built for comfort or style, it was built for functionality but it still didn’t change the fact that you were just as likely to be injured or killed by the Jeep than enemy action.
The same can be said for ships, they were designed for war not comfort and if you were a tall sailor a ship was a nightmare for you. Submarines were even worse.
Weapons were designed for one thing only and comfort took a back seat to functionality and usability and many weapons were not designed with the users comfort in mind.
Nobody mentioned Hugo Boss!
Yep, eg the nasty Mach tuck which even in passenger planes can be an issue. But then again jets are cool.