Zeitzler was almost exclusively a staff officer, serving as chief of staff in a corps, army, and army group. In September 1942, he was selected by Adolf Hitler as Chief of the Army General Staff, replacing Franz Halder. In early 1943 he was one of the key figures in the decision to launch Operation Citadel, the last major German attack on the Eastern Front, which ended in defeat. Zeitzler lost faith in Hitler's judgement, and abandoned his position in July 1944 after suffering a nervous breakdown. Zeitzler was regarded as an energetic and efficient staff officer, noted for his ability in managing the movement of large mobile formations.