After serving in the South African War (1899–1902) and in World War I, Dill advanced steadily, becoming director of military operations and intelligence at the War Office in 1934; he was knighted in 1937. Recognized as Britain's foremost strategist, he was head of a corps in France at the beginning of World War II, becoming chief of the imperial general staff in May 1940. He was largely responsible for the decision to reinforce Egypt with 150 tanks in August in spite of the shortage at home and backed Britain's intervention in Greece (March 1941). His greatest service to the Allied war effort, however, was as chief British military representative to Washington, D.C. (1941–44), where he helped coordinate the military policies of the two major western Allies. His friendship with the U.S. chief of staff, George C. Marshall, did much to cement Anglo-U.S. solidarity.