He served shortly after the war in Iraq, where took part in military action to put down the Iraqi revolt against the British, for which he received a medal for. Two years later, in 1920, Williams was in charge of an Officer Company of Gentlemen Cadets at the Royal Military College, Sandhurst, a role he undertook for four years. He attended the Staff College, Camberley from 1926 to 1927, alongside fellow students such as The Hon. Harold Alexander, Charles Hudson, Douglas Wimberley and Roy Bucher. Williams continued with the training theme, when in January 1929 he undertook duties as a General Staff Officer for weapon training at Aldershot Command. 1930 saw him promoted to brevet major, two years later he became a full major. 1930 also saw him take up a post which was to last four years with the Oxford University Contingent, Officer Training Corps. While undertaking the role he was promoted to lieutenant colonel, gaining the rank fully four years later in 1938. Williams served in Malta in 1937, and in 1938 he became the Commanding Officer (CO) of the 2nd Battalion, Rifle Brigade. He went on to lead them in operations in British Palestine during the 1936–1939 Arab revolt.