The evacuation of civilians in Britain during the Second World War was designed to save civilians in Britain, particularly children, from the risk of the 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. Further waves of official evacuation and re-evacuation occurred from the South and East coast in June 1940, when a seaborne invasion was expected, and from affected cities after the Blitz began in September 1940. There were also official evacuations from the UK to other parts of the British Empire, and many non-official evacuations within and from the UK. Other mass movements of civilians included British citizens arriving from the Channel Islands, and displaced people arriving from continental Europe.