The relations between the Holy See and Japan were informally established in 1919, when the Japanese government accepted a request by the Holy See to send an apostolic delegate to their country. It was not until 1942 that Japan began full diplomatic relations between the two states, making Japan the first Asian country to do so, and not until 1958 that the Japanese mission to the Vatican in Rome was upgraded to an embassy. The decision was made by Emperor Showa during World War II, hoping that the Vatican could serve as a mediator for negotiations between Japan and the Allies.

Pietro Fumasoni Biondi was an Italian prelate of the Catholic Church who served as prefect of the Sacred Congregation for the Propagation of the Faith in the Roman Curia from 1933 until his death in 1960. He was elevated to the cardinalate in 1933.