Hartmann was then transferred to the Hannover (1 October 1921 – April 1922) for onboard training and then to the training ship Niobe (April – 30 June 1922).[3] During this timeframe, he advanced in rank to Fähnrich zur See (officer cadet) on 1 April 1923 and to Oberfähnrich zur See (Senior Ensign) on 4 April 1925.[2]