forces in Iraq were combined into RAF Iraq Command in 1922, a joint services command aiming to use airpower as the core method of securing the country. Over the following year, manoeuvres and security operations gave Lindsay an early opportunity to experiment with armoured forces working in close co-operation with aircraft for support and resupply. He became a strong proponent of the new ideas of mechanised warfare, seeing it as a new and dominant paradigm in military strategy. In the summer of 1923, Lindsay was promoted to lieutenant-colonel in the Royal Tank Corps and made chief instructor of the Corps central school, where he became a leader in the nascent armoured-warfare movement within the Army. In 1926 he was appointed to the War Office as Inspector of the Royal Tank Corps and a member of the Mechanical Warfare Board, and from this position was able to work with J. F. C. Fuller to press the General Staff for the creation of the brigade-sized Experimental Mechanized Force in 1927. This held large-scale exercises in 1927 and 1928, demonstrating the practical utility of armoured units. Through the remainder of his time at the War Office and during his next posting, on the staff in Egypt, Lindsay continued to study the lessons of these exercises and influence the General Staff's position on armoured warfare. Returning from Egypt in 1932, Lindsay was given command of the 7th Infantry Brigade at Tidworth Camp, a motorised unit which had previously been the core of the Experimental Force. The culmination of his work with combined-arms forces was the end of the 1934 Army exercises, in which the 7th was used as part of an improvised armoured division led by Lindsay. However, the results were of limited success, partly due to personal disputes with Percy Hobart, who commanded the tank brigade and with whom Lindsay had had an acrimonious dispute. The immediate result of the failed experiment was to cut Lindsay off from the debate around the future of armoured warfare; he had recently been promoted to Major-General, and he would continue to rise in the Army, but he would no longer be involved with developing modern fighting doctrine. Senior command and the Second World War In 1935, Lindsay was posted to Calcutta to command the Presidency and Assam District in eastern India; he held the post until 1939, when he retired from the Army. In retirement, he