After the armistice, Ruge was an officer aboard the destroyer SMS B112, interned at Scapa Flow and in June 1919, he played a role in the scuttling of the German Fleet.

The V100 was the ship that rescued Grey from the water after the sinking and the pair became friends after meeting, their friendship only interrupted by World War II.

Ruge took command of FdM Ost, which provided minesweeping and escort support to the German Invasion of Poland in September–October 1939.

He was appointed as Naval Advisor to Field Marshal Erwin Rommel in November 1943 to supervise the defense of northern France from the predicted Allied invasion.

In August 1944, he became the Kriegsmarine's Director of Ship Construction, a position in which he served till the end of World War II.

Called out of retirement when Germany became a part of NATO, Ruge was appointed Inspector of the Navy (a position similar to the U.S. Chief of Naval Operations), a post he occupied until 1961.

Quoted at Normandy: Utilization of the Anglo-American air forces is the modern type of warfare, turning the flank not from the side but from above.