He served in a variety of posts until 1935, when he was promoted to captain and admitted to the War Academy for general staff training.

[1] During the Second World War he served as a general staff officer of the 25th Infantry Division from June 1940 to January 1943, and was promoted to major in 1940, lieutenant-colonel in 1943 and colonel in 1943.

In February 1943 he was assigned to the reserve of the Army Command and spent much of 1943 teaching at the military academy.

He commanded the Military Academy of the German Armed Forces from 1957 to 1959 and the Bundeswehr's 11th Panzergrenadier Division from 1959 to 1960.

Martin Selmayr has said that his commitment to the European project in part stems from a trip he took as a teenager with Gaedcke to the battlefields and military cemeteries of Verdun, where Gaedcke told him that his generation had an obligation to prevent any repeat of the mistakes of the past.