Basically - go see it. Great movie. No - fantastic movie. I've found Chris Nolan to be hit or miss - always beautifully filmed, but there are often plot holes you can drive a bus through that most people seem to miss because it all looks so good, and so much is thrown at you that you're overloaded. Inception and The Prestige are the two worst examples of this (so bad I've watched them twice..) while Interstellar has ridiculously awful science it pretends to adhere to, until halfway through it shifts to a "love conquers all" mode and rapidly descends to a giant cauldron of liquid poo in which it revels. Memento gets it right, sticking with a single theme and follows it through, while the first two Batman films are just brilliant (followed by an entertaining but not-as-good third).
Nolan loves to play with time in his films - Inception with its layers and ticking clock, Interstellar with the time dilation due (and ticking clock), Memento and the forward/backward storyline. He does the same in Dunkirk, with three storylines of a week, a day, and an hour in the lives of several Dunkirk participants, all intersecting in parts as they grow closer and closer together - and all through it, a ticking clock (literally) as the soldiers desperately try to get home.
I don't often get drawn in to films, but I found myself tense throughout, and Nolan manages to bring in a lot of tension as you sit on edge waiting for the next thing to go wrong. It's an exhausting film. More though, it gets over the utter powerlessness of almost all the participants, that they're simply statistics and at some point people are going to die, no matter their skill or preparation. This isn't an Arnie action film where the hero saves the day, this is about the horrors of war and how small and insignificant each person is, but also the intense bravery of many of these men in ways that no-one ever would know.
There's a Marie-Claire contributor who has been talking about how it's just a film glorifying war for men. Yeah, this glorifies war like Trainspotting glorifies taking drugs. It's hideous from nearly 80 years away.
As we exited the film, my wife recounted some stories of her grandfather, who was at Dunkirk. She had interviewed him as part of a school project. He was a remarkable man, I met him when he was in his early 90's, and I would have guessed he was in his 60's. Born in 1912, grew up in a children's home, joined the army when 18, served until the end of WWII, started a welding business then sold it and retired at 65 - got bored and started another one at 67 and ran it until he was 89. He didn't talk about what he did in the war, he even gave all his medals to a local museum to the horror of his family, as he thought no-one would care.
As part of this interview, he described running through the streets towards the beaches at Dunkirk, with men feet away from him being shot dead, and waiting for the evacuation. He was told he was brave but he said he never felt brave, all he did was try to survive. And that, in the end, was much of the point of the film, that these men survived and then later went back to fight again, that these seemingly small acts of what they couldn't see as bravery, mattered.
It also made me think of my wife's great uncle. He was on board the Royal Oak, a British battleship sunk by the Germans at the onset of WWII. Of the ~1200 crew, 833 were killed when it was torpedoed in Scapa Flow at the naval base in Orkney - her uncle, Billy, was one of the men killed. He was 16. Like the Arizona at Pearl Harbor, this site is now a war grave, and we were allowed to scatter the ashes of Billy's sister there. She never got over the loss of her brother. Another young man who tried to do what he could and serve, yet died almost the moment it began. The film reminded me that great feats aren't required to be a hero, that simply volunteering for a role that puts you in harms way for a greater good does that.
All that, so well filmed, and perfectly acted by every one of them, especially Tom Hardy. Never overplayed, just done right.
I'm not sure I've seen a film that conveys the horror and randomness of war, along with the personal sacrifice and bravery of the men who served.
Go see it.