Atonement's Context: Dunkirk Evacuation

One of the most shocking parts of the novel/movie is when they show the Dunkirk Evacuation. What's this? You may be asking yourself, so I'll put a brief summary of what was this action. 
It was 1940, in the middle of the Second World War, and Winston Churchill was in charge of the British troops. He decided to retire the military forces from the small town of Dunkirk, France, because the German army cut off the British, French and Belgian troops. 
Here is a video for you to learn more about the Dunkirk Evacuation.