Cawthorn served on the Staff of Baluchistan District as a General Staff Officer 3rd grade (GSO 3) from 15 December 1930 to 29 February 1932. He was appointed Deputy Assistant Quarter Master General (DAQMG) on the Staff of Western Command at Quetta 1 March 1932 to 20 January 1935. He served on the Mohmand operations on the North West Frontier in 1935. He was appointed a General Staff Officer 2nd grade (GSO 2) at the War Office in London from 6 January 1937 to 2 August 1939. On 3 August 1939 he was appointed a local colonel and temporary General Staff Officer 1st grade (GSO 1).