The Supreme Commander of the Allied Powers was Eisenhower, starting from December 1943, until July 1945. He began to create the command to execute Operation Overload. As the Supreme Commander he manages multinational, multidisciplinary military forces. This type of command means operational control over all land, air and sea forces. However, this title is given to the most senior commander within multinational military alliances, and it was established in the WWI.
