Which of the following countries wasn't an ally of Germany during WW II?

Greece was invaded by Italy from Albania on October 28, 1940. Benito Mussolini had seized Albania in the spring of 1939. Setting his sights on Greece, Mussolini sent an ultimatum to Greece demanding territory. Before the ultimatum expired, Italian troops poured across the Albanian-Greek border. It was a disaster for the Italians; Greek troops not only repulsed the invasion but eventually seized part of Albania.

Germany entered the battle on April 6, 1941 with its troops entering Yugoslavia and Greece from Bulgaria, Hungary, and Romania. All three nations were allied with Nazi Germany. Romania and Hungary later sent troops to be used in the invasion of the Soviet Union. Bulgarian troops occupied parts of Greece and Yugoslavia from 1941-1945.

Greece, with most of its troops fighting the Italian army, was outflanked by the German troops entering from the north. Even with the British providing air cover and ground troops, the Greeks were overwhelmed and defeated.