Mr. Nolan’s elastic approach to narrative works beautifully in “Dunkirk,” which oscillates among its three sections, each largely taking place in distinct locations in different time frames. The events on the beach — called the Mole for the breakwater that’s used as a dock — unfold during one week. The events on the sea occur in one day, while the air scenes transpire in an hour. The locations and the time periods are announced onscreen. At first the dividing lines aren’t always obvious as Mr. Nolan cuts from daytime scenes on the ground to those in the sea and in the air, a slight merging of space and especially of time that underlines the enormity of a fight seemingly without end.

Once Mr. Nolan begins switching between day and night, the lines dividing the three narrative segments mostly sharpen. Even as each section — with its individual dramas and perils — comes closer into view, Mr. Nolan keeps them all in dynamic play with one another. Some of this he achieves with stark visual echoes, as when water rushing into a downed Spitfire engulfs the pilot and elsewhere a soldier nearly drowns. (Tom Hardy plays the most critically important pilot, while a sympathetic Jack Lowden takes on a critical support role.) At one point, Mr. Nolan pulls the three narrative strands tightly together, creating a tremendous, enveloping sense of bone-deep dread.

“Dunkirk” is a World War II movie, one told through soldiers, their lived and near-death experiences and their bodies under siege. Names are generally irrelevant here; on the beach — and in the sea and air — what counts are rank, unit, skill and the operation, although more important is survival, making it through another attack and somehow avoiding exploding bombs. Mr. Nolan’s emphasis on the visceral reality of Dunkirk leaves much unsaid; even in some opening explanatory text, the enemy isn’t identified as Nazi Germany. The soldiers, of course, know exactly who they are fighting and perhaps even why, but in the field the enemy is finally the unnamed stranger trying to kill them.