Greece during World War I

At the outbreak of World War I in August 1914, the Kingdom of Greece remained a neutral nation. Nonetheless, Greek forces in October 1914 occupied Northern Epirus, a territory of southern Albania that it claimed for its own, at a time when the new Principality of Albania was in turmoil. At the same time, the Kingdom of Italy occupied Sazan Island, another Albanian possession, and later that December the Albanian port of Vlorë.

Greece had signed a defense treaty with the Kingdom of Serbia in 1913 that obliged Greece to come to Serbia's aid if it were attacked from the Kingdom of Bulgaria. When Bulgaria began mobilization against Serbia in 1914, the Greek Prime Minister Eleftherios Venizelos believed that he could get Greece to join the war on the side of the Allies if they landed 150,000 troops in Salonika. Venizelos failed to bring Greece into the war on the Allied side. His explanation that this was because King Constantine I was a "German sympathiser". The king and the anti-Venizelists (opponents of the prime minister) were opposed to joining the war and argued that the Serbo-Greek Treaty was void if one of the great powers fought alongside Bulgaria. However, British, Australian and New Zealand ships and troops were allowed to use the island of Lemnos as a base from which their attack on Gallipoli was mounted in 1915 (see Gallipoli Campaign). Venizelos was unconstitutionally removed from office by the king on 5 October 1915, only to return to the political scene in October 1916.

Venizelos invited a joint Franco-British (and later also Russian) expeditionary force, formed in part by withdrawals from Gallipoli, transforming Salonika into an Allied military base. (Keegan 253) Forces began to arrive on 3 October 1915. In the early summer of 1916, the Athens government under King Constantine handed over Fort Rupel to the Germans, believing it a neutral act, though claimed as a betrayal by the Venizelists. Nonetheless, the Allies still tried to swing the official Athens government to their side. From their positions in Greece, Allied forces (British, French, Russian, Italian, and Serb troops) fought the war from Greek territory, engaging Bulgarian forces when they invaded Greece in August 1916 in the Battle of Struma.

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