Help with a similar movie.

They were a bunch of American soldiers (commandos) sent to a forest for training. Then for some reason -- disapproving of vietnam war, as I vaguely remember -- They were being hunted one by one by the military and killed. The forest was filled with death traps. The deaths were very gruesome. None of them survived at the end. It was highly controversial towards the government. It was probably made before 1992 and after 1982.