In the vast majority of war movies, the act of combat is a show of force in which the stronger side wins, barreling through the enemy’s defenses like a bowling ball. But in “The Wall,” war is like a protracted game of chess, where each side is down to its final pieces on the board, and strategy matters.

A lean, back-to-basics thriller from director Doug Liman (who made the original “The Bourne Identity”) and first-time screenwriter Dwain Worrell (whose tricky script landed on the Black List), this wide-release Amazon Original film pits a pair of American snipers against an unknown foe, who just might be the notorious Iraqi sniper known as Juba, aka “the angel of death” — an adversary with 75 U.S. casualties notched on his belt, and countless others unconfirmed.

As this high-tension standoff escalates, we never learn who the mystery shooter is, though this much is certain: The two American soldiers would do well not to underestimate their opponent. As written, he’s a lot smarter than they are, and a much better shot. While that imbalance may rankle those who consider war movies like sporting events, expecting to see some aspect of their side confirmed as superior, it makes for much better drama — for instance, “The Day of the Jackal,” or the sharpshooter villain played by Vincent Cassel in the recent Liman-produced “Jason Bourne.” Besides, how often do we get to see the American Army portrayed as the underdog?

When Army Ranger staff sergeant Shane Matthews (WWE star John Cena) and his spotter, Allan “Ize” Isaac (Aaron Taylor-Johnson), arrive on the scene of a distress call, everybody on site is dead. Observing from a safe distance, they count eight corpses and see no sign of life. It’s 2007, and the Iraq war is officially over, but as they’ll soon find, not everyone has laid down his gun.

Studying the scene through a malfunctioning spotting scope, Ize suspects they may be witnessing the handiwork of an Iraqi sniper, but his commanding officer isn’t so sure. The place looks deserted to him — just an oil pipeline through empty desert, surrounded by construction equipment. The only thing they can’t see around is a rickety stone wall, all that remains of some native Iraqi structure.

Impatient and over-confident, Matthews walks down to the site while Ize covers him from his camouflaged spot on a nearby hill. And then, in one of those moments whose seeming inevitability merely compounds the terror, a shot is fired and Matthews hits the dirt, badly wounded. Putting his own life at risk to save his comrade, Ize rushes to the scene, taking a bullet in the leg in the process.

While Matthew bleeds out in the sand, Ize barely manages to pull himself to (temporary) safety behind the stone wall, where nearly the entire movie takes place, with Ize pinned down hoping for backup he has no way of reaching. When he tries to contact base, he discovers his radio is broken — a convenient plot contrivance but one that forces him to switch to a local frequency, where his would-be assassin is waiting to taunt him.

With its single-location, practically real-time idea of a one-on-one confrontation between two snipers, “The Wall” belongs to a select pool of tête-à-tête thrillers — “Phone Booth,” “Buried,” “Sleuth” — in which our hero discovers he’s the mouse being hunted by a sly cat and must use his wits if he hopes to survive. (Worth noting: The villain has no face, and the hero’s name is pronounced “Eyes.”) To Liman’s credit, the director wasn’t interested in a strictly high-concept exercise, and Cena’s character effectively raises the stakes by giving Ize a chance at redemption. Yet the conceit is double-edged, since the source of Ize’s anguish merely confuses matters when it’s finally revealed.

While the Iraqi sniper pries for personal details on the radio, Ize tries to keep him talking, listening for clues that might betray his location (the sound of flapping sheet metal, for instance) and hoping he’ll slip up in some way that will turn the situation in his favor. This part is the most enjoyable, but also the most far-fetched, and though Liman did his best to capture the gritty you-are-there quality of Iraq (by shooting on anamorphic 16mm near Edwards Air Force Base in Lancaster, Calif.), he might as well have staged the entire thing on a stripped-down theater stage.

“The Wall” succeeds because of Worrell’s words, which cleverly circumvent obvious plot holes — like Ize’s broken radio, or the way it suddenly works when the story requires — while using an implausible English-language conversation between opposing snipers to keep the tension high and conjure a mental picture of this unseen adversary.

In the end, it’s up to Taylor-Johnson (and to a lesser degree, voice actor Laith Nakli as the Iraqi sniper) to sell those words, and the young actor gives a terrific performance under extreme conditions, totally convincing as a man alternating between panic and trust in the practical discipline of his training. If he’s going to survive, it’s that training, not luck, and certainly not the flimsy cover provided by the wall, that will protect him.