On the day that Winston Churchill replaced Neville Chamberlain as prime minister, Germany invaded Holland and Belgium. Despite all the efforts of the Allied armies, Hitler's powerful Panzer divisions smashed their way through to the French coast. For the retreating British Expeditionary Force, Dunkirk was the only practical point of departure, and on May 26, the order for total evacuation, Operation Dynamo, was given. Over succeeding days, the "miracle" of Dunkirk took place, and almost 400,000 troops were rescued from the beaches. Meanwhile, in Britain, belated preparations were going on for the expected invasion: the Battle for Britain had begun.