Trapped behind enemy lines in Scotland circa 117 A.D. and besieged by the savage Picts, a dwindling handful of Roman soldiers battles to survive. Were this a Ridley Scott movie, 180 bloated minutes long, the $200 million budget would’ve gone to computer effects, helicopter shots, and Russell Crowe. But frugal writer/director Neil Marshall (Dog Soldiers, The Descent) makes do with much, much less. And does better. His story could equally well be set in the Old West or Afghanistan right now; and he doesn’t pretend it’s mythic. It’s just a framework, really, for an extended chase across snowy Scottish peaks and through misty forests (a literal fog of war). The genre? Lost platoon. Versatile, muscled Michael Fassbender (Hunger, Eden Lake) plays the only Roman likely to survive; what camaraderie exists among his motley band of seven survivors is, we know, going to disintegrate under stress. They are imperialists on the run in foreign terrain, which the pursuing natives intend to wet with their blood. (Most frightening among them is a mute savage, played by model/Bond girl Olga Kurylenko, who beheads her captives like Al Qaeda.) Are there any surprises in Centurion? Not really: It proceeds by steady, satisfying winnowing. Those who should die, die. Talk is incidental. There’s one kind woman, an outcast herbalist “witch” (Imogen Poots), who offers brief reprieve. And back at the stockade, betrayal awaits. All very familiar and efficient. John Ford would approve.