Das Boot
I think it's one of the few reliable war films simply because it's apolitical. This may seem insignificant, but nowadays, every historical film, whether from the East or West, is influenced by propaganda, albeit slightly. However, in Das Boot (any edition), there is no hidden agenda, just the simple horror of war. It's a film that speaks clearly and without mincing words, with a rawness rarely seen in other films.
Another striking feature of the film is its precision and attention to detail. I am no naval expert, yet I could still pick up on details such as the nautical cartographer counting the proximity bombs launched by the destroyer. They spent almost 30 million marks on it, but they spent it well.