 At the time of the German invasion , Greece was at war with Fascist Italy , following the Italian invasion on 28 October 1940 . The Greeks joined the Allies and defeated the initial Italian attack and the counter @-@ attack of March 1941 . When Operation Marita began on 6 April , the bulk of the Greek Army was on the Greek border with Albania , then a protectorate of Italy , from which the Italian troops had attacked . German troops invaded from Bulgaria , creating a second front . Greece had already received a small , inadequate reinforcement from British Empire forces in anticipation of the German attack , but no more help was sent afterward . The Greek army found itself outnumbered in its effort to defend against both Italian and German troops . As a result , the Bulgarian defensive line did not receive adequate troop reinforcements and was quickly overrun by the Germans , who then outflanked the Greek forces at the Albanian border , forcing their surrender . The British Empire forces were overwhelmed and forced to retreat , with the ultimate goal of evacuation . For several days , Allied troops played an important part in containing the German advance on the Thermopylae position , allowing ships to be prepared to evacuate the units defending Greece . The German Army reached the capital , Athens , on 27 April and Greece 's southern shore on 30 April , capturing 7 @,@ 000 British Empire forces and ending the battle with a decisive victory . The conquest of Greece was completed with the capture of Crete a month later . Following its fall , Greece was occupied by the military forces of Germany , Italy and Bulgaria . 
