Bodewin Keitel was born on 25 December 1888 in Helmscherode, the son of a landowner. He was the brother of Wilhelm Keitel, later a field marshal and head of the High Command of the Wehrmacht. Bodewin joined the army in 1909 and served during World War I. After the end of World War I, he was retained in the Reichswehr, eventually reaching the rank of colonel. In 1937, he was appointed as the Chief of Training Department ("T4") and was added in the General Staff of the Army.
