The war had profound consequences on the health of soldiers. Of the 60 million European military personnel who were mobilised from 1914 to 1918, 8 million were killed, 7 million were permanently disabled, and 15 million were seriously injured. Germany lost 15.1% of its active male population, Austria-Hungary lost 17.1%, and France lost 10.5%. In Germany, civilian deaths were 474,000 higher than in peacetime, due in large part to food shortages and malnutrition that weakened resistance to disease. By the end of the war, starvation caused by famine had killed approximately 100,000 people in Lebanon. Between 5 and 10 million people died in the Russian famine of 1921. By 1922, there were between 4.5 million and 7 million homeless children in Russia as a result of nearly a decade of devastation from World War I, the Russian Civil War, and the subsequent famine of 1920-1922. Numerous anti-Soviet Russians fled the country after the Revolution; by the 1930s, the northern Chinese city of Harbin had 100,000 Russians. Thousands more emigrated to France, England, and the United States.
Question: How many years were European military personnel mobilised?
Answer: 4