In 1920, Marden was given command of the British division occupying Constantinople. During the Chanak Crisis of 1922 he played a key role in negotiating a peaceful settlement between British and Turkish forces, for which he later received a knighthood. He returned home in 1923 to become GOC of the 53rd (Welsh) Infantry Division, a Territorial Army (TA) formation, before retiring in June 1927. He held the ceremonial colonelcy of the Welch Regiment from 1920 to 1941.