Ah, the military comedy. Once a staple, not hard to find. Here's a good one that's both a forgotten movie and an even better forgotten book (which I've read twice and may read again). Both book and movie had a big influence on my life because the division of people into schnooks and yulds seemed to me to explain so much about my own personality.
The plot is pretty complicated. Dick Shawn is a schnook. When anything can go wrong for him, it will. Because of a complicated series of events, he appears to have served only one day in the military in WWII (The Big One), though he served much longer and spent two years in a prison camp. As a result of the mistake, he's drafted again and sent to a Japanese island in the middle of nowhere. A wild and crazy Ernie Kovacs is the commanding officer, which tells you a bit about how things are there. There are 100 Americans stationed on the island, and they have little to occupy their time. The Japanese who live there don't like the Americans and in fact still have a shrine to a downed Japanese plane.
The cast is great and has a lot of fun with the concept. Don Knotts has another great military comedy turn (the first is in No Time for Sergeants), and Kovacs is Kovacs. The plot, as I said, is complicated, but the schnookish Shawn finally turns his life around. Just thinking about this one makes me want to pull out the book again. Or maybe the movie's on Netflix. I checked. No such luck.