After his father's death, his uncle Oskar von Zalewski, a soldier, became very close to Erich and told Erich to become a soldier. In November 1914 Erich von Zalewski asked to join the Prussian army, and was one of the youngest soldiers and remained a soldier fighting for the army until the end of World War I. He was wounded twice, and was given the Cross of Honor (Ehrenkreuz) and then Iron Cross.