After the War, Dittmar entered the Reichswehr and continued to serve with engineers units, where he reached the rank of Colonel (Oberst) to the date of April 1, 1936.

With the outbreak of the World War II, Dittmar served as a commander of the engineer school in Berlin-Karlshorst.

He was posted to the Army High Command Leader Reserve in October 1941, and became General for Special Employment in April 1942.

In that post, which he held over the remainder of his war service, he was the Official Military Commentator of the German Armed Forces.

A rumour that he committed suicide in April 1945 was dispelled on the 23rd when he surrendered to soldiers of the 30th U.S. Infantry Division at Magdeburg.