With the outbreak of the World War I, Hampe was called up in August 1914 and assigned to a machine gun-detachment; he was posted to the Guard Corps and ordered to the Western front. He participated in the First Battle of Ypres, the First Battle of Champagne, the Gorlice–Tarnów Offensive, and the Battle of Verdun. His military service ended on November 30, 1919, when he retired from the Army. During his service in the Army, Hampe was awarded with the both classes of Iron Cross and Hesse Medal for Bravery.