Greece entered the Second World War on the side of the Allies following an Italian invasion from Albania on 28 October 1940. Greece repulsed the initial Italian attack and a counter-attack in March 1941. Coming to the aid of its struggling ally, Nazi Germany launched an invasion of its own known as Operation Marita, which began on 6 April. While the bulk of the Greek Army was deployed on the Albanian front, German troops invaded from Bulgaria, creating a second front. The Greek army found itself outnumbered in its effort to defend against both Italian and German troops. As a result, the Metaxas defensive line did not receive adequate troop reinforcements and was quickly overrun by the Germans, who then outflanked the Greek forces at the Albanian front, forcing their surrender.