For an ‘EVENT THAT SHAPED OUR WORLD’–emphasis their’s, not mine–I readily admit that I have never heard of this particular conflict in World War II, though I don’t know if that’s due to a failing of the American education system or a de-emphasis of it because it doesn’t seem to directly involve the United States.
Having read on the Dunkirk evacuation on Wikipedia I assume it to be the latter because, while the United States did fight in WWII, we weren’t a part of this particular episode.
That being said, I enjoy War films, though looking at the trailer I hope the movie has occasional elements of the miraculous and bizarre (which may be present, just not in the trailer) like Apocalypse Now because I can think of nothing as surreal as war, where extreme acts of inhumanity and brutality play out side by side with those of remarkable heroism and bravery.
Dunkirk is directed by Christopher Nolan (The Dark Knight, Inception) so I expect this movie to be very grounded, which is a pity.