Director Sam Mendes says making the war drama "1917" has been the most exciting job of his career.

"The first time I understood the idea of war was when my grandfather told me about his experiences in the First World War. This film is not a story about my grandfather, but rather the spirit of him -- what these men went through, the sacrifices, the sense of believing in something greater than themselves," Mendes said.

"Our two main characters are sent on a dangerous journey through enemy territory to deliver a vital message that could save 1,600 soldiers, and our camera never leaves them. I wanted to travel every step and breathe every breath with these boys, and cinematographer Roger Deakins and I discussed shooting ‘1917' in the most immersive way. We designed it to bring audiences as close as possible to their experience. It's been the most exciting job of my career," he added.

The war drama tells the story of two young British soldiers at the height of the war. It stars George MacKay as Lance Corporal Schofield and Dean-Charles Chapman as Lance Corporal Blake who are given an impossible task to deliver a message deep in the heart of enemy territory that, if successful, would save the lives of 1,600 British soldiers. For Blake, the assignment is personal as his brother is one of the 1,600 men who will die if they fail.

It also stars Colin Firth and Benedict Cumberbatch. The film will stream on SonyLIV on Friday.