During the Second World War, after the conquest of mainland Greece by Nazi Germany in April 1941 (which was followed by the conquest of Crete in June), Serres was assigned by the Nazis to their Bulgarian allies (along with the rest of East Macedonia and Thrace and the island of Thasos), who occupied the city until the Allied liberation of Greece in 1944. In 1943, Serres' Jewish population was deported by the Gestapo to the Treblinka death camp and exterminated. There was a significant resistance movement in the city during the occupation, led by the left-wing National Liberation Front (EAM).