Due to the start of World War I, Hippke's regiment was sent to the Eastern front as a part of the 36th Reserve Division under the command of Generalleutnant Kurt Kruge (). Hippke subsequently participated in the Battle of Gumbinnen and the Battle of Tannenberg. In September 1915, he was transferred to the Division Staff and appointed Adjutant to the Division Surgeon. In this capacity, Hippke was promoted to the rank of Oberarzt ("Oberleutnant") on October 13, 1915 and saw combat in Galicia.