Born in Munich, Bavaria, his father, Eduard, was a landscape painter; as was his grandfather. His family soon moved to the spa city of Bad Tölz. After he left school Schleich decided to enroll in the Bavarian Army's cadet program and in 1909 was commissioned into the 11th Bavarian Infantry Regiment. Before the outbreak of the First World War, Schleich was plagued by medical problems and was released from active duty. He volunteered again and on 25 August 1914 was badly wounded in the Battle of Lorraine.