70s - 80s Vietnam War/Zombie Horror Movie Help!
I’m trying to identify a movie I saw years ago (mid 80s), but I only remember the basic premise.
The characters enter what I remember as a cave or underground bunker system that spirals downward into the earth. At different levels there seem to be Vietnam War-era military bunkers or encampments. Everyone seems to understand that the bunker/cave is dangerous because they come decked out in military gear and weapons.
The place is inhabited by undead/zombie soldiers, possibly both American and Vietnamese soldiers from the Vietnam War. Once the characters enter, they’re chased through the underground complex by the dead soldiers.
The part I remember most clearly is that the cave/bunker system seems to change or rearrange itself. Once you’re inside, you can’t simply retrace your steps because the passages have changed, so the entrance can no longer be found. For instance, at one time the characters decide to dig up through the ceiling of one room to try and bypass everything and go straight to the entrance. But once they went through the hole, they were in a random room deeper in the bunker system.
It had a horror/supernatural feel rather than being a straightforward war movie. Does this sound familiar to anyone?