Millard Harmon was born in the United States in 1888. He attended the West Point Military Academy and graduated in 1912 (74/95) and joined the United States Army. He learnt to fly and served with the French Air Service during the First World War.

By the outbreak of the Second World War Major General Harmon was placed in charge of the 2nd Air Force. In January 1942 he chief of staff of the United States Air Force.

In July 1942, Harmon was appointed chief of US Army Forces in the South Pacific. The following year he took command of New Georgia.

Harmon was made head of all USAAF units in Pacific in August 1944. Millard Harmon died when his aircraft crashed on 26th February 1945 while on route to Hawaii.