After attending Eton and the Royal Military College, Sandhurst, Pollok was commissioned into the 15th Hussars in 1903.

[2] He served in World War I with the Australian Forces in Gallipoli and then transferred to the Irish Guards in 1916.

[2] He became Commanding Officer of 1st Bn Irish Guards in 1917, receiving a promotion to acting lieutenant colonel in the process.

[3] After the War he attended the Staff College, Camberley from 1920–1921, was appointed Brigade Major for the 1st Guards Brigade at Aldershot Command and then, in 1926, he was re-appointed Commanding Officer of 1st Bn Irish Guards.

[2] He was appointed General Officer Commanding Northern Ireland District in 1938[4] and GOC 43rd (Wessex) Infantry Division in July 1940.