Roosevelt was Secretary of the Navy prior to his entering politics. Prior to the reformulation of the Presidential cabinet after WWII you had the Secretary of War (in charge of the Army - land warfare) and the Secretary of the Navy (The Navy and the Marines; and during wartime the Coast Guard). Those who held these positions formulated policy, helped to define what were the strategic interests, and also were integral contributers to the overall strategies of the two services during wartime. So Roosevelt in my opinion should have a modicum of aggression as one of his "traits". Today each service has its own secretary (the Marines do not as they are part of the Navy) who fall under the jurisdiction of the Secretary of Defense.