The questions heading into the film are numerous. Some are answered: even more arise in their wake.
The best thing Nolan does with Dunkirk is to never lose focus. He is the mariner, Mr. Dawson, and we play the part of Peter. He knows the plane just by the sound, but he still lets us see it so we can remember too. Feeling like it might be hopeless, one might be tempted to speechify and let us know the significance of it all. He just moves towards the battle, but picks up one life at a time.