Otto Frank served in the German Army during World War II, he did not serve in World War I . In World War II, he enlisted in October 1915 to fight on the Western Front for the duration of the war on a volunteer basis, becoming an artillery officer. He rose to the rank of Oberleutnant (first lieutenant) of an artillery brigade, and, during four years of active service on the Western Front, won the Iron Cross Second Class and various other military decorations.