I finally got to see this, and it was intense! I only have a vague knowledge of the battle/rescue there, and I'm sure some liberties were taken, but it kept me on the edge of my seat, wondering who would make it and how. Unfortunately, like many war movies (or any movie where all the characters have essentially the same uniform), I had no idea who was who among the soldiers. Well, except Kenneth Branagh, of course. Our three main soldiers had similar builds, and dark hair, and barely spoke. I'm still not entirely sure who was on the train at the end, except I guess not the French soldier.
Mark Rylance was wonderful, as usual, as was our pilot who survived. I admit I did scoff slightly at the magical pilot at the end -- amazing how he could land perfectly like that. It might have been a better choice to ditch over the sea, but I suppose we needed to see that some people were captured.
I also was not aware of the timeline thing before I saw the movie, so I was confused at first, despite the title cards telling me that one story line started 1 week out, one 1 day out, and one 1 hour out. I knew they'd all come together in the end, but I had to keep reminding myself that these night time scenes were a couple of days before the small boats were launched.
I might have to see it again to catch the bits I missed.