General Douglas MacArthur, the Army's Chief of Staff, believed that the 1921 mobilization plan was based on unsound assumptions and that the Army required active field army headquarters before the start of any mobilization to manage the integration and training of subordinate units as they mobilized. He also concluded that the existing three army area/six army arrangement was too ponderous to field a force that might be needed in a hurry and that existing mobilization plans were not flexible enough to tailor to various war plans then in existence.