Between the wars, he was a lecturer at the Staff College, Camberley and the Imperial Defence College, where Brooke knew most of those who became leading British commanders of the Second World War. From the mid-1930s Brooke held a number of important appointments: Inspector of Artillery, Director of Military Training and then GOC of the Mobile Division. In 1938, on promotion to lieutenant-general he took command of the Anti-Aircraft Corps (renamed Anti-Aircraft Command in April 1939) and built a strong relationship with Air Chief Marshal Hugh Dowding, the AOC-in-C of Fighter Command, which laid a vital basis of co-operation between the two commands during the Battle of Britain. In July 1939 Brooke moved to command Southern Command. By the outbreak of the Second World War, Brooke was already seen as one of the British Army's foremost generals.