It's only got two actors - Lee Marvin, and Toshiro Mifune. It's about two soldiers during World War II, fighting each other on a desert island, and eventually finding common ground. Marvin and Mifune were in fact both soldiers in WWII, on opposite sides. It was remade as an SF novella and film called Enemy Mine.
It's a sparse, arty, film, with a lot of theatrical staring and glowering. A lot of close-ups of eyes, like in Spaghetti Westerns. There isn't much dialogue, and Mifune speaks Japanese throughout with no subtitles. The atmosphere reminded me of The Thin Red Line. I personally liked it, but I can understand it would irritate a lot of viewers. There are apparently two versions, and I think the version I saw must be the theatrical release, which has a stupidly abrupt ending; the director's cut may have a better resolution.
The acting of course, from two utter giants, is very good: Boorman gets marvellous performances from them. It's strange to turn from something like this to the sort of hammed-up nonsense Lee Marvin was expected to deliver in The Dirty Dozen and films like that.