Anyone acquainted with Carol Reed’s 1947 classic “Odd Man Out,” which starred James Mason as an Irish rebel on the run in an unnamed UIster city easily identifiable as Belfast, will recognize Yann Demange’s debt to it in “’71,” which reverses things by focusing on a British soldier trying to survive on his own in the hostile Catholic part of the city in 1971 after becoming separated from his squad during a street riot. It’s not the equal of Reed’s masterpiece, nor frankly is Jack O’Connell, who plays the soldier, as remarkable as James Mason was as Johnny MacQueen. But both are quite good nonetheless, and the picture is certainly far preferable to Robert Alan Aurthur’s “The Lost Man,” which attempted to translate Reed’s tale into an American civil rights context by presenting Sidney Poitier as a robber trying to elude the cops pursuing him.

O’Connell, in a part that shows his star quality far better than his lead role I Angelina Jolie’s “Unbroken,” plays Gary Hook, a raw recruit who grow up in a group children’s home in London. He’s first seen, in uniform, enjoying a final afternoon with his younger brother Darren (Harry Verity), who still lives there, before shipping out. But at the last minute his squad is reassigned to Belfast, where they’re put under the command of Lieutenant Armitage (Sam Reid), who seems as green as they are. Eschewing heavy armor and firepower when the soldiers are sent into a Catholic area in support of the heavy-handed local police, Armitage can’t contend with the violence that erupts, leaving behind two of his men in a rushed escape. One, Hook’s buddy Thompson (Jack Lowden), is beaten by the irate crowd and shot to death by an IRA gunman, and Gary would have suffered the same fate had he not bolted and run into the narrow, labyrinthine alleyways, closely pursued by the shooter and his comrades.

What follows is a series of encounters with locals, not unlike those that Mason’s MacQueen had in “Odd Man Out,” though Gregory Burke’s script skips any romantic entanglements and instead emphasizes the deadly rivalries that existed among not only the two sides in Northern Ireland but also the factions within them. On the one hand those fissures pit the old—line IRA leadership, represented by the world-wise, compromising Boyle (David Wilmot) against the younger, more radical wing led by the defiant, reckless Quinn (Killian Scott). On the other, the British military contingent led by Armitage and his more seasoned corporal (Babou Ceesay), are at the mercy of the undercover counterintelligence force that includes Captain Browning (Sean Harris) and Sergeant Lewis (Paul Anderson), who aren’t above colluding with the enemy when it suits their purposes and are concerned about what Hook might learn of their operations during his time on the streets.

As for Gary, his frantic efforts to escape assassination put him first into the hands of a foul-mouthed nine-year old loyalist (Corey McKinley), who takes him to a bar where Protestant paramilitaries have an operations center, and after a violent incident there, into those of a Catholic father-and-daughter team, Eamon (Richard Dormer) and Brigid (Charlie Murphy), who tend to his wounds while fretting over which IRA faction to deliver him to. Everything comes to a head in a deteriorating high-rise where the wounded soldier is stalked by Quinn as his men as Boyle, Browning, Lewis, and Armitage all converge on the place with different goals in mind.

Demange keeps the plot convolutions relatively clear (though the machinations of the counterintelligence force vis-à-vis the so-called Ulster Defense Force remain a mite murky), but those elements are really secondary to the action-oriented aspects of the story, which he handles with an assurance that belies the fact that this is his first feature. The sequences of Hook running through Belfast’s narrow streets are raw and vital, abetted by the superior hand-held work of cinematographer Tat Radcliffe, Chris Wyatt’s crisp editing and David Holmes’ propulsive score; and the final confrontation sequence is atmospherically carried off, even if a final twist involving conflicted a conflicted young radical named Sean (Barry Keoghan) comes across as a bit too much of a statement about the cynicism imbedded in the Troubles. O’Donnell is central to the picture’s success, giving Hook a convincingly human center while pulling off the role’s considerable physical demands with aplomb, The rest of the cast is solid down the line, with Wilmot and Scott persuasively etching two sides of the rebel coin, just as Harris, Anderson and Reid embody different aspects of the British character. And while Dormer and Murphy affectingly show the anxiety of people of essentially good will trapped between merciless forces, young McKinley effortlessly steals every scene he’s in. Mention has to be made of the Lancashire and Yorkshire locations that stand in for Belfast, which Radcliffe uses to full effect, and the unexaggerated period detail built into Chris Oddy’s production design, Nigel Pollock’s art direction, Kate Guyan’s set decoration and Jane Petrie’s costumes.

In sum, “’71” is a terrific action movie that also says something painfully true about the deceit and double-dealing that poisoned people’s lives during the years of conflict in Northern Ireland.