From May 26 to June 4, 1940, the evacuation of Allied troops from the French port of Dunkirk and its surrounding beaches, known as Operation Dynamo, was a hugely important event in the history of World War II. Had Dynamo not succeeded, Winston Churchill, who had come to power only 16 days before Dynamo began, would almost certainly have lost his premiership, and been dismissed as a dangerous fantasist and warmonger, and the British government forced to negotiate an armistice with Germany. In the event, the evacuation turned out to be a success beyond even the wildest dreams of its most enthusiastic promoters, who had hoped to rescue at most 45,000 troops but by the end of the 10-day exercise had plucked more than 300,000 soldiers from the piers and beaches of Dunkirk—including, as it happens, my father, then a very green 21-year-old second lieutenant in the Royal Artillery, who, less than a year before, had been a failed teacher in a state elementary school west of Birmingham in the Black Country.

Dynamo was first and foremost an intricate and complex naval operation in which each new day's tactics had to be spontaneously improvised, with every day expected to be the last. The beaches that extend east and west of Dunkirk are very shallow and gently shelving, but the ships capable of carrying large numbers of soldiers, from passenger ferries to naval destroyers, were deep-drafted, needing at least 14 feet and more to stay afloat. So fleets of much smaller boats, drawing four feet six inches or less, were needed to bridge the gap between the lines of wading troops, standing up to their shoulders in cold seawater (about as cold as Puget Sound in May), and the ships that would bring them back to England, just over 25 nautical miles across the Channel.

Once aboard the ships that would take them to Dover, Ramsgate, Folkestone, and Harwich, the soldiers were told never to speak of what they'd seen at Dunkirk, for fear of the damage it would cause to morale at home. This enforced silence enabled a powerful national myth, still alive today, which began when Churchill, addressing the House of Commons on June 4 (the last day of the evacuation), called Dunkirk "a miracle of deliverance." According to the myth, this miracle was accomplished by the small-boat owners of England, from yachtsmen to bank clerks to inshore fishermen, coming together, dropping all distinctions of rank and class, to rescue the nation in its hour of need. The small boats that ferried the waders out to the ships were sentimentally rechristened "the little ships" that saved the British Army.

Most of the myth is hooey, but there's a grain of truth in it. Small boats really were needed, and the Admiralty had an unquenchable thirst for them, scouring the harbors and estuaries of England for every rowing boat ("pulling boat" in naval parlance) and small motor cruiser they could find. As the photos from May and June in 1940 show, most of the "little ships" were towed out to Dunkirk, in rafts of many dozens at a time, by oceangoing tugs. In 1949, an official naval report on the operation found that one of its notable weaknesses was the failure to appoint a skipper of each boat who would pilot it back and forth between the waders and the ships. What actually happened was that everyone in the boat would climb out onto the scrambling net on the ship's side, leaving the boat to drift away on the tide, never to be seen again. So every morning there'd be cables from Dunkirk to Dover (where Vice-Admiral Bertram Ramsay presided over Operation Dynamo, closely advised by the Admiralty in London), begging for yet more small boats.

After the war was over, the survivors of Dunkirk would almost all liken it to Hell. It was Hell on earth, a living Hell. Those rescued from the beaches via the "little ships" had by far the worst of it. Those rescued from the outer breakwaters (or "moles") had a rather easier time. My father was lucky. His commanding officer, Captain Jimmy Styles, had been killed by a German artillery shell on the outskirts of Brussels in Belgium, and my father, as the only commissioned officer in the troop, had safely led his men to Dunkirk's perimeter canal, where they set up their 18-pounder guns (left over from World War I) and fired them until they ran out of ammunition. They then spiked the guns, which rendered them unusable by the enemy, and clambered into, went on top of, and clung to the sides of a single 8-cwt truck, and drove into Dunkirk, where their arrival coincided with the beginning of an air raid by the Luftwaffe, which made them take cover in an already-crowded basement of a ruined and still-smoldering four-story house. As soon as the all clear was sounded, the troop was ordered to march at the double to a destroyer that was just about to cast off from the eastern mole. HMS Esk was responding to a Mayday call from the Scotia, a passenger ferry that had taken a direct hit (a 1,000-pound bomb from a Stuka that fell clean down the aft funnel and exploded in the engine room) and was sinking fast by No. 6 buoy in the harbor approaches, with around 2,000 French soldiers aboard.

The Scotia was going down by the stern. The destroyer came nearly alongside and then gently nudged the ferry bow-to-bow so that the French evacuees gathered on the forward deck could safely walk or jump from ship to ship. Others were already in the sea, waiting to be picked up by the Esk's lifeboats or swimming for the scrambling nets that were being unfurled from both sides of the destroyer. When the Stukas returned to rake the decks of the Scotia and her rescue vessels with machine-gun fire, the Esk's gun crews managed to keep the aircraft at bay. In all, nearly a thousand evacuees were saved by the Esk, and more were then picked up by another destroyer, the Worcester.

My brother William tells me that our father once told him of how he was met by a sea-sodden French army officer whom he hauled over the Esk's rail and planted on the deck. Not a word of thanks for this assistance, only a furious tirade of abuse of the British for saving themselves and leaving the French to die or be taken prisoner on the Dunkirk perimeter. That story nicely illustrates just how fractious relations between the Allies had become by June 1, 1940, the day on which my father escaped from Dunkirk. Everybody blamed everybody else. The French blamed the British for being, as ever, perfidious Albion. The British blamed the Belgians for being all too ready to surrender, the French for their poor morale, and, most unjustly, their own air force, the RAF, for failing to sufficiently protect the soldiers from the Luftwaffe.

The question is this: How do you present Hell on earth, Hell in the air, and Hell at sea on celluloid? For Christopher Nolan, much of the answer is do it in ultra-high-definition 70 mm IMAX film and show it in IMAX cinemas, which he has done before with movies like the Dark Knight films and Interstellar, repeatedly arguing the case for restoring the "theatrical experience" to moviegoing. Dunkirk is meant to be a nonstop 114 minutes of unalleviated spectacle, a massive collage of beautifully composed pictures, each one lasting for only a few seconds, of gunfire, flames, drowned corpses, exploding bombs, aerial dogfights with numerous plane crashes, and more, much more. The soundtrack includes a constant ticking noise, which might be the sound of a palpitating heart or that of a clock registering the suspense of passing time. The film's cast is British-stellar, with two theatrical knights (Sir Kenneth Branagh and Sir Mark Rylance) and, for good measure, a teen heartthrob rock star, Harry Styles (sans his famous hair). It also has a PG-13 rating, which tells us something important about the nature of this sensational action movie.

Nolan is now one of the greatest and most inventive movie technicians. He also lists the Argentinian writer Jorge Luis Borges near the top of the people who influenced him, which signals his taste for cerebration, and can be seen in some of his earlier movies, like Memento and Insomnia. But the most Borgesian quality in Nolan's work is his cool detachment from the world he describes. Dunkirk shows a world full of terror, but Nolan goes to great lengths to ensure that his audience is never terrified. We sit in our seats munching popcorn and watch other people undergoing terrifying experiences.

Case in point: A soldier in the water is crushed to death by the immense tonnage of a warship, loosely tied to the dock, as it drifts against the pilings. We see in close-up the bow of the ship as it slowly closes with the wooden pier, and hear a panicked scream, abruptly truncated, as someone's rib cage gets unceremoniously flattened. Another case in point: Two soldiers wading in the sea encounter two corpses floating facedown in the water; the live men casually push the dead men aside and continue on their way. It's all right, we never met the guys who drowned, and, anyway, they're either stuntmen or just uniforms stuffed with inflated airbags, so who cares? Dunkirk is a film whose own artifice is always front and center.

Watching Dunkirk, I was again and again reminded of Wilfred Owen, the British poet who was killed, aged 25, in the final week of World War I, and wrote, "My subject is War, and the pity of War. The Poetry is in the pity." That is the problem with Dunkirk: It is too hurried, too eager to move on to the next shot, from sea to sky, from sky to the soldiers on the beach, to bother with the pity.

In all this hurry, the only actor given a chance to develop into a real character is Mark Rylance, as Mr. Dawson, a middle-class, cardigan-wearing Everyman of retirement age, who might have been a local bank manager or civil servant. Rylance equips him with a West Country burr in his accent (Dorset or Devonshire would be my guess). Dawson owns a tubby sloop-rigged motor sailer, Moonstone, perhaps 30 feet long, hears the call to duty on the BBC, so heads to France with a young man and an underage boy for crew. As they close with Dunkirk, they spot the lone survivor (Cillian Murphy) of a wrecked Thames barge, sitting on its upturned stern, which exposes an enormous propeller. A line is thrown from Moonstone to the survivor and they haul him in. There's a second lieutenant's single pip on his epaulets, and he crouches, shivering and wordless, in a corner of the cockpit, where the crew put a blanket around his shoulders. Mr. Dawson makes the kindly observation that the man is suffering from shell shock, which reveals that Dawson himself is a survivor, of the First World War. That is the closest that this movie ever comes to pity as Owen meant it, and it doesn't come nearly far enough.

Nolan, disappointingly, subscribes to the myth of the "brave little ships," though the film also recognizes the important role of the RAF and that of the Royal Navy. For me, the daftest (and most enjoyable) scene is when Kenneth Branagh, playing Commander Bolton, the senior naval officer who has had up till now little to do in his naval overcoat and fetching roll-neck sweater, except affect an air of gravitas (which looks a lot like boredom), claps his binoculars to his eyes to view what looks like a regatta of incoming historic wooden boats, all freshly varnished and with gleaming brightwork. On one boat, an elegant woman stands by the shrouds dressed as if for a summer cocktail party (perhaps she's meant to be Britannia). For the first time in the movie, Branagh's mouth cracks slowly into a smile.

He's asked what he can see. "Hope" is his reply.

I was sitting in the Boeing IMAX theater with both Charles Mudede and my daughter Julia, also a movie reviewer for The Stranger, and they both agreed that Branagh said "Home." Maybe they're right and I'm wrong, or maybe home and hope have somehow congealed into the same word, each meaning the other and vice versa, at least in the context of Operation Dynamo.

When interviewed recently in the New York Times, Christopher Nolan said: "Dunkirk, for whatever reason, has never been addressed in modern cinema." That's not right. Atonement, directed by Joe Wright in 2007, and adapted from Ian McEwan's 2001 novel of the same name, must have slipped Nolan's mind. Atonement is not exclusively about Dunkirk, but the evacuation occupies roughly a third of the movie and is a brilliantly imaginative reconstruction of what happened there.

Private Robbie Turner (played by James McAvoy) has a first-class degree in English literature from Cambridge, but was later publicly disgraced and imprisoned. During the retreat from Belgium, he's been adopted by two corporals, Nettle and Mace (played by Daniel Mays and Nonso Anozie), who at once defer to him and mock him for his lowly rank. As this trio breast the last sand dune before the sea, they stop to stare at the beach below them, and one of the corporals mutters, "Fuck me, it's like something out the Bible!" And so it is. It might be the Israelites crossing the Red Sea in their flight from Egypt, so many soldiers are there—in looping lines, in huddles, in ragged platoons with, here and there, the occasional wandering solitary. We're at Bray-Dunes, the village just east of Dunkirk, from where many thousands of wading evacuees were taken by small boats to the ships lying offshore. By contrast, Nolan's beaches look absurdly underpopulated and impossibly clean. These beaches are strewn with shit, rucksacks, military hardware, cars, trucks, dead bodies, bomb craters, and all the clobber of a defeated army.

The surreal, five-minute-plus tracking shot that follows is rooted in Robbie's delirium, his fever brought on by dehydration and a worsening shrapnel wound in his side, hidden by his shirt, but it is also the delirium of war itself. In the far distance, a Ferris wheel slowly revolves; we see tiny human figures hanging dangerously from its cars, seemingly providing the wheel with its motive power by redistributing their own weight. Beyond that, smoke rises from the burning oil refinery at Dunkirk. We pass (in no particular order) soldiers in fistfights; an officer killing horses with his service revolver—a single shot to the brain of each animal; soldiers, some in their underpants, others in battle dress, running to the sea; a small congregation of soldiers, several with bandaged heads, singing the hymn "Dear Lord and Father of Mankind" on a tatty seafront bandstand; a French civilian pushing his bicycle along the promenade, then turning it around and going back the way he came; two more civilians, a mother comforting her daughter as they sit together on the sand; soldiers aboard a children's merry-go-round, pushing it with their feet; a soldier methodically busting the radiators of a line of jeeps with his rifle butt (leave the engine on, and it will eventually seize up and wreck the vehicle); five or six horsemen galloping down the main street and onto the promenade; a soldier, stripped to his underwear, patiently sunbathing as if this was a weekend at Brighton; a soldier exercising on a pommel horse, presumably looted from a gym; a soldier weeping as he sits on the running board of a civilian car; more fistfights; a supercilious and unhelpful naval lieutenant; a stranded Thames barge, her tan sails torn to ribbons, either by the wind or by machine-gun fire. The shot continues until we reach a bar, emptied of every last drop of liquid of any kind, but still full beyond capacity with soldiers, led by a banjoist, singing "Fuck 'em all! Fuck 'em all! The long and the short and the tall..." Nothing in the shot is explained, but it is eloquent on the brutal incongruities of war and its eerie mix of the ordinary and the horribly extraordinary.

I can easily imagine 12-year-old boys leaving the theater after watching Dunkirk and saying it's the best action movie ever made. And so, perhaps, it is. But the R-rated Atonement is by far the truer and the deeper of the two, as I think my father would have recognized, had he lived long enough to see it. recommended