In peacetime the Greek Army contained about 32,000 men. However, during the Balkan Wars (1912-13) this was increased to 210,000. Senior officers were strongly royalist and like King Constantine I tended to support Germany in its disputes with Britain.
On the outbreak of the First World War, the Greek 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 King Constantine I refused to agree, he resigned from office.
When Eleftherios Venizelos was re-elected after a landslide victory in March 1915, he ordered the mobilization of the Greek Army. Over 150,000 men were called up and most of them were sent to help defend the borders of Serbia. When Venizelos invited the Allied forces to Salonika he was dismissed by King Constantine I.
Eleftherios Venizelos escaped to Crete where he formed a provisional revolutionary government. With the support of Allied forces at Salonika, Venizelos made plans to march on Athens. In June 1917 King Constantine I was deposed and Venizelos was able to regain power.
On 29th June, 1917, Eleftherios Venizelos declared war on the Central Powers. The 60,000 soldiers recruited by Venizelos in Crete, provided the core of the new army. Eventually 250,000 Greek soldiers saw action in the war, including the highly successful Vardar Offensive. During the war, the Greek Army had around 15,000 men killed and another 85,000 wounded.