WARNING: SPOILERS

“’71,” from first-time feature-film director Yann Demange and first-time feature film writer Gregory Burke, is intense and unrelenting. Twenty minutes in, our main character, British soldier Gary Hook of Derbyshire (Jack O’Connell), whom we’ve seen: 1) survive basic training, 2) pal around with his kid brother, and 3) share a cigarette with a corporal, gets lost behind enemy lines. Meaning he gets left behind in the western, Irish Catholic part of Belfast during “the Troubles.” He’s already seen his mate, Thommo (Jack Lowden), get his head blown off by the IRA, and in the shock afterwards, and it’s a shock for everybody, he’s on the run. Literally at first: dashing through alleys and over walls. It’s all that basic training paying off, and he finally finds sanctuary in a crummy outdoor toilet where he sweats and gasps and rests until nightfall, then steals some clothes and tries to make his way back to safety.

But his long night is just beginning.

Hook depends upon the kindness of strangers. A tough Protestant kid takes him to a friendly, Loyalist pub; but while he’s waiting to get picked up by members of the MRF, the British army’s counter-insurgency unit, Loyalists in the backroom, with a bomb for the IRA, screw up and blow themselves up along with the pub. There goes the tough kid. Hook, dazed, wounded, and distraught over the death of his young helper, wanders the streets before collapsing against a wall. There, he’s found by Eamon (Richard Dormer) and his daughter Brigid (Charlie Murphy), who have this exchange:

Brigid: Leave him be.
Eamon: Can’t.

That’s nice. Although it’s not until they get back home, in the Catholic section, that they realize Hook is a British soldier.

Burke and Demange create a complex, morally ambiguous world. You root against the IRA hotheads, who are trying to kill Hook, and for a more senior, diplomatic man, Boyle (David Wilmot), who orders them to stand down. Except Boyle is in collusion with the bastards of the MRF (including Sean Harris, the villain of “Mission: Impossible – Rogue Nation”), who also want Hook dead, since he may have seen them at the Loyalist pub and don’t want that fiasco traced back to them. It’s a world where good deeds go punished.

The movie is refreshingly anti-Army but pro-soldier. At one point, Eamon, who did his own stint, calls the Army, “Posh cunts telling thick cunts to kill poor cunts,” which will remind American viewers of the Vietnam-era line “the white man sending the black man to kill the yellow man.” Eamon also says, in words that Sean Penn’s great soliloquy at the end of “The Thin Red Line,” “It’s all a lie. They don’t care about you. You’re just a piece of meat to them.” As the movie will prove. The Army is just another corporation, with middle managers protecting their territory.

“’71” is a simple, straightforward story about a complex situation. It’s also about a simple situation that is sadly universal: we fight, we fight, we fight. The Army is simply the modern corporation that channels this human tendency. When Hook is recovering, and in conversation with Brigid, he tells her he’s from Derbyshire and she says she has cousins in Nottingham. He pauses, then this exchange:

Hook: It’s just that Derby and Nottingham don’t get along.
Brigid: Why not?
Hook: I don’t know really.