Greece entered the Second World War on the side of the Allies following an Italian invasion from Albania on 28 October 1940. The following year, on 6 April, Nazi Germany launched an invasion of its own from Bulgaria known as Operation Marita; Athens was occupied on 28 April and the resistance on the Greek mainland had ceased by the 30th. King George II and his government had left the Greek mainland for Crete five days earlier. The island was in turn attacked by a Nazi airborne invasion on 20 May 1941. The Germans prevailed after seven days of fighting, forcing an Allied withdrawal to Egypt.