 Eastwood transferred back to the British Army on 17 October 1918, and in 1919 he served in the ill-fated North Russia Intervention, as brigade major on Lord Rawlinson's staff.After further staff duties at Aldershot, Cork in Ireland, and attended the Staff College, Camberley from 1921 to 1922, and served on the staff at the War Office in London, before becoming an instructor at the Staff College, in 1928.Following a spell as Commanding Officer (CO) of the 2nd Battalion, King's Royal Rifle Corps, he was appointed Commandant of the Royal Military College, Sandhurst, with the rank of major general in 1938.