The second son of King Constantine I, Alexander was born in the summer palace of Tatoi on the outskirts of Athens. He succeeded his father in 1917, during World War I, after the Entente Powers and the followers of Eleftherios Venizelos pushed Constantine I, and his eldest son Crown Prince George, into exile. Having no real political experience, the new king was stripped of his powers by the Venizelists and effectively imprisoned in his own palace. Venizelos, as prime minister, was the effective ruler with the support of the Entente. Though reduced to the status of a puppet king, Alexander supported Greek troops during their war against the Ottoman Empire and Bulgaria. Under his reign, the territorial extent of Greece considerably increased, following the victory of the Entente and their Allies in the First World War and the early stages of the Greco-Turkish War of 1919–1922.