On this day in 1917, several weeks after King Constantine I abdicates his throne in Athens under pressure from the Allies, Greece declares war on the Central Powers, ending three years of neutrality by entering World War I alongside Britain, France, Russia and Italy.
Constantine, educated in Germany and married to a sister of Kaiser Wilhelm II, was naturally sympathetic to the Germans when World War I broke out in the summer of 1914, refusing to honor Greece's obligation to support Serbia, its ally during the two Balkan Wars in 1912-13. Despite pressure from his own pro-Allied government, including Prime Minister Eleutherios Venizelos, and British and French promises of territorial gains in Turkey, Constantine maintained Greece's neutrality for the first three years of the war, although he did allow British and French forces to disembark at Salonika in late 1914 in a plan to aid Serbia against Austro-Hungarian and Bulgarian forces.
By the end of 1915, with Allied operations bogged down in Salonika and failing spectacularly in the Dardanelles, Constantine was even less inclined to support the Entente, believing Germany clearly had the upper hand in the war. He dismissed Venizelos in October 1915, substituting him with a series of premiers who basically served as royal puppets. Meanwhile, civil war threatened in Greece, as Constantine desperately sought promises of naval, military and financial assistance from Germany, which he did not receive. After losing their patience with Constantine, the Allies finally sent an ultimatum demanding his abdication on June 11, 1917; the same day, British forces blockaded Greece and the French landed their troops at Piraeus, on the Isthmus of Corinth, in blatant disregard of Greek neutrality. The following day, Constantine abdicated in favor of his second son, Alexander.
On June 26, Alexander reinstated Venizelos, who returned from exile in Crete, where he had established a provisional Greek government with Allied support. With a pro-Allied prime minister firmly in place, Greece moved to the brink of entering World War I. On July 1, Alexander Kerensky, the Russian commander in chief and leader of the provisional Russian government after the fall of Czar Nicholas II the previous March, ordered a major offensive on the Eastern Front, despite the turmoil within Russia and the exhausted state of Kerensky's army. The offensive would end in disastrous losses for the Russians, but at the time it seemed like a fortuitous turn of events for the Allies, in that it would help to sap German resources. The following day, Greece declared war on the Central Powers.
The new king, Alexander, stated the case for war dramatically in his official coronation address on August 4: "Greece has to defend her territory against barbarous aggressors. But if in the trials of the past Greece has been able, thanks to the civilizing strength of the morale of the race, to have overcome the conquerors and to rise free amidst the ruins, today it is quite a different matter. The present cataclysm will decide the definite fate of Hellenism, which, if lost, will never be restored." Over the next 18 months, some 5,000 Greek soldiers would die on the battlefields of World War I.