 So here's the summary. So the Allies knew they had to invade Europe. Hitler knew the Allies were going to invade Europe. So this was all going to come to a head at some point. Hitler prepared by building a massive defensive line along the Atlantic and the Baltic Sea coast called the Atlantic Wall. But it stretched for 800 miles. I mean, it was a massive undertaking with barbed wire and defensive positions and pillboxes and firing positions, et cetera, et cetera.