I think I watched this 3-5 years ago on a DVD from the library. The setting is a set of trenches, I'm pretty sure in World War I. A group of English speaking soldiers storm the other side's trenches, only to find them largely deserted. As they explore the trenches, they find go on and on without end or a ladder to climb to the surface. Some of them start to disappear as they fall back. They run into some enemy soldiers (German?), and I think kill at least one who has surrendered to them. Eventually, they have truth revealed to them that they are in Hell (I think with something speaking to them through a dead enemy's lips) due to their past sins, and I think one of them is offered a way to go home, because they're innocent, or at least not nearly as guilty.
I watched this in the United States, in Pittsburgh, checked out from the library. Unfortunately, my wife and I watch most of our films from the library, so searching my history isn't terribly feasible. The title of Downfall comes to mind, but that's a different film about the last days of Adolf Hitler.