In April 1927 he became First Secretary to
Vincent Massey, head of the
Canadian Embassy in
Washington, DC. Wrong joined the newly expanded Canadian Department of External Affairs around the same time as fellow future star diplomats
Lester Pearson,
Norman Robertson, and
Hugh Keenleyside; this expansion was engineered by
Oscar D. Skelton. Wrong served in the
League of Nations and in 1938 he represented Canada at the
Évian Conference. In 1941 he went to Washington when
Leighton McCarthy was made Ambassador, then 71 years old. That made Hume the
de facto head of the delegation for Canada in Washington, performing such duties as implementation of the
Ogdensburg Agreement. He articulated the principle of
functionalism in 1942 as follows: :The principle, I think, is that each member of the grand alliance should have a voice in the conduct of the war proportionate to its contribution to the general war effort. A subsidiary principle is that the influence of the various countries should be greatest in connection with those matters with which they are most directly concerned. The placement of
C. D. Howe on the
Combined Production and Resources Board, and of other seats on the
Combined Food Board, were evidence of the practice of functionalism. In the estimation of
Jack Granatstein, "Canada’s massive war effort, coupled with its tough advocacy of the functionalism principle, made it one of the leaders of the middle powers for a few years during and after the war." In 1946 Hume Wrong was appointed
Canadian Ambassador to the United States and he remained in the post until 1953. He was one of the key architects of the
North Atlantic Treaty, which would give rise to
NATO. He later rose to become the Canadian Undersecretary of External Affairs and was named undersecretary to
NATO, but died before he could take up the post. ==Death==