This is a piece of war propaganda showing the true cost of the British home front as an allegory for the American experience. That being said this movie is immensely heartfelt and human to its core. You care deeply about these characters and that's why you care about the war effort. It's completely unlike today's Dunkirk which uses the war effort as a means of exploring heroics and character. This film starts with the characters and then leads us into their involvement in the war effort showing how the effort was driven by people rather than the effort motivating people to get involved.
I would argue this film is also far more accurate in depicting the role of the civilian armada in helping save the British troops at Dunkirk. It shows the blurring of that line between civilian and combatant in WW2 in what was a far more Total War than WW1. This line becomes extremely clear when the Nazi soldier lands in her backyard and she is forced to become part of the war despite her desire to stay out of it.
This film is all about fighting, manliness, and conquering in the name of freedom. It was necessary to convince the home front to put up what was an extraordinary fight.
Incredibly good film. Scenes in movies are getting longer and more compelling. The directors are figuring out how to create tension through ingenious scene work and not just plot work or associative editing work.