A CERTAIN audacity is essential when making a war movie. Consider the task. The dead and living must be honoured, their sacrifices set out, their bravery and terror conveyed. The unimaginable horror of war must be made to seem real to those of us fortunate enough to live a peaceful life. Who dares think they are up to that job?

Sam Mendes did, and the result is magnificent.

The story, inspired by the experiences of Mendes’s grandfather, is simplicity itself. Lance corporals Schofield and Blake, played by George MacKay and Dean-Charles Chapman, are ordered to venture into enemy territory with a message telling a British colonel to stop a planned attack. A trap has been set by the Germans, and if the order does not get through some 1600 lives are at risk. Among those waiting to go over the top is Blake’s brother.

With that, two hours of thrilling, heart-pounding cinema begins as the two boys – for that is what they are – try to make it through no man’s land and on to their destination. Mendes co-writer is Krysty Wilson-Cairns, who trained at the Royal Conservatoire of Scotland, and if this screenplay doesn’t make it into the Oscar nominations it will be a travesty indeed. Wilson-Cairns is not the film’s only Scots connection: many scenes were shot in Glasgow.

Mendes shoots the film as if in one continuous take. It is actually lots of long scenes cleverly stitched together. Whatever, the approach gives the film the pace of a thriller. Minute by minute, the tension is ramped up, aided by a pulsating score from Thomas Newman. Roger Deakins, like Newman, part of Mendes’s Skyfall crew, is in charge of cinematography, helping to make a film that sweeps from epic to intimate.

This is the First World War as depicted elsewhere, but bolstered by strange, original, unforgettable images. Heaven and hell are in the details. Everywhere lies death, and rats the size of dogs. “Bloody hell,” says Blake on encountering one particularly large rodent in an abandoned German bunkhouse that’s relatively luxurious compared to the British trenches, “even their rats are bigger than ours”.

It is a measure of the riches on show that the cast boasts actors of the calibre of Benedict Cumberbatch, Mark Strong, Colin Firth and Andrew Scott, all playing small parts. Also on screen for a relatively brief time is Claire Duburcq, the only woman among a sea of men. Her part in the story may be small but it is of towering importance.

At the heart of everything are MacKay and Chapman, with the former a standout. That wide open face of his is made for the big screen, and across it, and Mendes’s canvas, every emotion flows. Superb.