Joseph Grew was born in Boston, Massachusetts on May 27, 1880. He served as the US Minister to Denmark from 1920 to 1921 and the US Minister to Switzerland from 1921 to 1924. In 1924, Grew became the Under Secretary of State and oversaw the establishment of the Foreign Service. Grew was the US Ambassador to Turkey from 1927 to 1932 and the US Ambassador to Japan from 1932 to 1942. In 1944, Grew resumed his post as Under Secretary of State.

Grew served as Acting Secretary of State for most of the period from January to August 1945 as Secretaries of State Edward Stetinius and James Byrnes were away at conferences. Among high level officials in the Truman Administration, Grew was the most knowledgeable of Japanese issues, having spent so much time in Japan.

Grew was a member of the "Committee of Three ," along with Secretary of State Henry Stimson and Secretary of War James Forrestal. This group sought to find an alternative way to make Japan surrender without using atomic bombs. Assistant Secretary of War John McCloy drafted a proposed surrender demand for the Committee of Three, which was incorporated into Article 12 of the Potsdam Declaration. The original language of the Proclamation would have increased the chances for Japanese surrender as it allowed the Japanese government to maintain its emperor as a "constitutional monarchy." Truman, who was influenced by his Secretary of State James Byrnes during the trip by ship to Europe for the Potsdam Conference, changed the language of the surrender demand. Grew knew how important the emperor was to the Japanese people and believed that the condition could have led to Japanese surrender without using the atomic bombs. Grew stated, "If surrender could have been brought about in May 1945 or even in June or July before the entrance of Soviet Russia into the war and the use of the atomic bomb, the world would have been the gainer."

Grew died in 1965.