WATCH: Benedict Cumberbatch and Colin Firth in Trailer for Sam Mendes' War Movie '1917'

The first trailer for Sam Mendes' eagerly-anticipated war movie 1917 has arrived, and it's super-intense stuff.

The trailer shows Colin Firth's character, a military leader, issuing a mission that's literally a matter of life and death to a couple of young soldiers played by rising stars George MacKay (Captain Fantastic) and Dean-Charles Chapman (Game of Thrones).

"Your orders are to deliver a message calling off tomorrow's attack. If you don’t, we will lose 1,600 men, your brother among them," Firth's character warns sternly.

“If you fail, it will be a massacre,” he adds, underlining the seriousness of the orders.

Later in the trailer, we get a glimpse of another military leader played by Benedict Cumberbatch. “There is only one way this war ends,” his character says ominously. “Last man standing.”

Check it out below.

The movie's all-star cast also includes Cumberbatch's Sherlock co-star Andrew Scott, Bodyguard's Richard Madden, Kingsman's Mark Strong, Good Omens' Daniel Mays, and Harry Potter and the Cursed Child's Jamie Parker.

It's Mendes' first movie since his pair of Bond films, Skyfall and Spectre. He co-wrote the screenplay with Krysty Wilson-Cairns, a former screenwriter on Penny Dreadful.

1917 is due to open in select theaters on December 25 before getting a wider release on January 10, which gives us plenty of time to prepare for what looks like a nerve-shredding watch.

Are you looking forward to seeing Sam Mendes's 1917?