Some good ones mentoned, but I'll toss a couple more in for consideration.
The Great Escape.
Master and Commander.
The latter may not rate as a classic, but both of them qualify for me on the grounds that the characterisation and attitudes are realistic for the times.
One of my pet peeves is the way that Hollywood so frequently portrays military men in unrealistic ways.
I'm well aware that competence and professionalism don't make as much dramatic impact as emotionalism, agonising and shouted disputes... but the latter grate.
I grew up around a couple of retired officers who'd seen both world wars. Both of the were self-disciplined to a high degree and left me with a lasting respect for the military.
I thought it detracted from Saving Ryan's Privates that the attitudes of the characters involved owed more to the 1990s than the 1940s. ... That and the shot of the squad moving through what was supposedly enemy territory - walking across the middle of open ground, bunched up and looking at each other while talking in normal conversational tones. :banghead:
Similar Hollywood stuff-up (Big Red 1??) has the troops under artillery fire .... and some idiot running around amongst exploding shells and flying debris yelling "Take Cover!"
I mean,,, yanks aren't really that stupid. Are they?
It takes more than a lot of explosions and fake blood to make a good war movie.
Regards......... Cooch