During World War I, Blamey served as a staff officer in Egypt, at Gallipoli, and on the Western Front. He rose to the rank of brigadier general in 1918. Following the war, he served on the Imperial General Staff. In 1925, Blamey retired from the regular army and became chief police commissioner in Victoria, Australia, while remaining a general in the militia.
Blamey resigned his police position in 1936 following a minor scandal in which he lied under oath to protect the reputations of two women who were victims of robbery. Shortly after the beginning of World War II, he rejoined the regular army, was promoted to lieutenant general, and was assigned command of I Corps. Serving in Egypt in 1940 under General Archibald P. Wavell, he oversaw the evacuation of Australian troops from Greece following the German invasion of that country in April 1941. Promoted to full general in September 1941, Blamey became commander in chief of Australian forces in March 1942.
Under orders from General Douglas MacArthur, who was concerned about the Japanese occupation of Buna in Papua and a possible invasion of Australia, Blamey took personal command of the ground forces and led them in the recapture of Buna in January 1943. He also held personal command in September 1943 in a campaign that took the city of Lae and liberated the eastern New Guinea coast. Following these actions, Blamey found himself relegated to a background role as MacArthur assumed more control of Allied armies in the theater.
As the Allies island-hopped closer to Japan, Blamey undertook operations against isolated Japanese troops in islands bypassed by MacArthur. These actions, bereft of significant naval and air support, proved costly and were criticized by many as unnecessary, but Blamey believed that it was in Australia's interest that these occupied islands be freed. At the end of the war, he signed the Japanese surrender document as the Australian representative. Discharged in January 1946, he was promoted to field marshal in June 1950. Blamey died at Melbourne on 27 May 1951.
Gallaway, Jack. Odd Couple: Blamey and MacArthur at War. Queensland, Australia: University of Queensland Press, 2000.; Hetherington, John. The Life of Field Marshal Sir Thomas Blamey. Melbourne, Australia: Cheshire, 1954.; Horner, David. Blamey: The Commander in Chief. Sydney, Australia: Allen and Unwin, 1998.