Watch the Explosive Final Trailer For World War I Epic ‘1917’

“If you fail, it will be a massacre.”

The vast drama of World War II eclipsed the fact that the First World War, which lasted from 1914 through 1919, was a vicious, blood-soaked buzzsaw of a conflict, one that shattered the minds of those whom it didn’t also destroy physically. Sam Mendes’s 1917, it seems, is here to remind us that the Great War was its own particular kind of hell. 

The movie is notable for the solid gold reviews it has already received prior to U.S. release—it currently has a 94% “Fresh” rating on Rotten Tomatoes—and for director Mendes’s choice to shoot it as if it is a single two-hour cut. For 120 minutes the audience is plunked down in the middle of World War I and unable to look away. 

The end result has been described as almost literally breathtaking, and the trailer, which features major British stars like Colin Firth and Benedict Cumberbatch, reflects that, as it manages to communicate both the unnerving nature of a pitched battle and the urgency the soldiers at its center (George MacKay and Dean Charles Chapman) feel as they set out on their mission. 

And what a mission. Colin Firth’s general puts it succinctly to the soldiers in the trailer: “If you fail, it will be a massacre.” So no pressure, right? Here’s the synopsis:

At the height of the First World War, two young British soldiers, Schofield (Captain Fantastic‘s George MacKay) and Blake (Game of Thrones‘ Dean-Charles Chapman) are given a seemingly impossible mission. In a race against time, they must cross enemy territory and deliver a message that will stop a deadly attack on hundreds of soldiers–Blake’s own brother among them.

It’s really that straightforward, and by all accounts, totally harrowing. 

1917 opens in limited release in the U.S. on December 25.