Constantine, eldest son of George I (1845-1913) was born in Athens on 2nd August 1868. Educated in Germany, Constantine married Sophia, the sister of Kaiser Wilhelm II in 1889. As Crown Prince, Constantine led the Greek Army to victory in the Balkan Wars (1912-13). Constantine became the King of Greece after the assassination of his father in Salonika on 8th March 1913.
On the outbreak of the First World War, Greek's prime minister, Eleftherios Venizelos, favoured an alliance with Britain, France and Russia against the Central Powers. Venizelos wanted Greece to give military aid to the Allies during the Dardanelles campaign, and when the king refused to agree, he resigned from office.
When Eleftherios Venizelos was re-elected after a landslide victory in March 1915, he ordered mobilization of the Greek Army. When Venizelos invited the Allied forces to Salonika he was dismissed by the king. Venizelos returned to Crete where he formed a provisional revolutionary government.
With the support of Allied forces, Eleftherios Venizelos made plans to march on Athens. In June 1917 the king decided to hand the Greek throne over to his second son, Alexander, who reigned until dying from a monkey bite in October 1920.
A plebiscite in December 1920 voted overwhelmingly for Constantine's return. However, his popularity was only short-lived and after the Greek Army failed against the Turks in Anatolia and Smyrna in 1922, he was forced to abdicate.
Constantine died in exile in Sicily in 1923.