The evacuation of civilians in Britain during the Second World War was designed to protect people, especially children, from the risks associated with aerial bombing of cities by moving them to areas thought to be less at risk. Operation Pied Piper, which began on 1 September 1939, officially relocated more than 3.5 million people. There were further waves of official evacuation and re-evacuation from the south and east coasts in June 1940, when a seaborne invasion was expected, and from affected cities after the Blitz began in September 1940.