When the war broke out in the summer of 1914, the Greek King Konstandinos (Constantine), whose wife was the sister of the German Kaiser, insisted on neutrality by Greece, but the allies pressured Greece to join with them against German and Turkey, holding out the carrot of land in Asia Minor, where large populations of Greeks lived, especially in the coastal cities of Konstantinoupoli (Constantinople) and Smyrni (Smyrna).
There were also Greeks living in the inland areas of Kappadhokia (Cappadocia) and more up by the Black Sea, the latter called Pontic Greeks ( from the old Greek word for sea, Pondos).
Venizelos, the Prime Minister, wanted to join the Allies, and the prince, Alexander, who replaced his father Konstantinos when he left Greece in 1917, was also in favor of this, the goal being liberation of the Greeks ain both Thrace and Asia Minor. Venizelos set up a revolutionary government in Thessaloniki, and in 1917 Greece entered the war in the socalled ‘Macedonian campaign’, allied with the British, French, and Serbians.
With the defeat of Turkey and Bulgaria, Greece occupied Thrace and Venizelos demanded the largely Greek region of Smyrni (Smyrna) at Versailles. With the acquiescence of the Allies he moved troops into Smyrni in May of 1919, his stated purpose the protection of the half million Greeks living there, but the following year he lost the elections in Greece and monarchist factions took over around the same time that support from the Allies vanished, some say because they did not want to alienate the Turks.