A teenage soldier becomes separated from his platoon in the cauldron of violence that is 1971 Belfast in Yann Demange's nail-biting survival thriller.

Punctuated by kinetic action sequences that relentlessly tighten the knot of tension in our stomachs, '71 is a dazzling debut from the TV director, who made the acclaimed Channel 4 series Top Boy.

Demange puts leading man Jack O'Connell through the physical wringer as he explores the sectarian divide through the eyes of a wet-behind-the-ears recruit, who is marked for death by the provisional IRA and supposed allies.

Juddering handheld camerawork during chase sequences and a nerve-racking game of hide-and-seek keep us uncomfortably close to the carnage, and only a few hours after the stricken soldier has foolishly assured his kid brother that this first tour of duty will be a breeze: "I'm not leaving the country so you've got nothing to worry about."

Home is where the heartbreak is.

Squaddie Gary Hook (O'Connell) completes his gruelling training and is immediately dispatched to the Northern Irish capital to facilitate the fragile peace.

Under the command of platoon leader Lieutenant Armitage (Sam Reid), Gary and fellow recruits head to the Catholic west.

At first, hostility amounts to little more than potty-mouthed children throwing water bombs full of urine.

However, a house-to-house search spirals out of control and during the subsequent riot, Gary and pal Thommo (Jack Lowden) are left behind.

A small gang of provisional IRA comprising ruthless leader Quinn (Killian Scott), sidekick Haggerty (Martin McCann) and newbie Sean (Barry Keoghan) shoot Thommo at close range but Gary escapes, sprinting down alleyways with the gun-toting assailants in pursuit.

Thankfully, Gary finds sanctuary and as night falls, he traces a path back to the barracks under cover of darkness.

A boy called Billy (Corey McKinley) offers assistance but when the tyke's makeshift plan goes horribly wrong, Gary turns to Brigid (Charlie Murphy) and her father, Eamon (Richard Dormer), a former army medic, who has had his fill of the uniform.

"You're just a piece of meat to them," Eamon warns Gary.

'71 masterfully sustains tension without getting bogged down in the thorny politics of the era.

Nerves are shredded to tatters in the opening half hour and screenwriter Gregory Burke wrings every drop of suspense from his neat set-up.

A detour to a loyalist pub is orchestrated and edited with brio.

O'Connell follows up his bruising portrayal of a young offender in Starred Up with another emotionally charged performance, holding his character's fears at bay until that particular dam bursts and sobs rack his aching body.

Lines between allies and adversaries are repeatedly blurred, stacking the odds heavily against Gary as he ducks for cover, and we hunker down with him, brows beaded with sweat and knuckles white with fear.