What did the “V” signify in V-J Day, the 1945 Allied celebration of Japan's defeat?

The “V” in V-J Day signified “Victory over Japan.”

V-J Day is the common Allied term for the celebrations marking Japan's surrender in World War II. In the United States and several other countries, the main celebrations followed the announcement of Japan's acceptance of the Potsdam Declaration on August 14–15, 1945. The abbreviation mirrors V-E Day, which marked victory in Europe after Nazi Germany's surrender.

The expression can refer either to August 15, when Japan's surrender was announced, or to September 2, when Japanese representatives signed the formal Instrument of Surrender. This difference reflects two separate milestones: the political decision to end the war and the legal ceremony that completed the capitulation.

The term was especially prominent in wartime newspapers, public celebrations, and photographs of crowds in Allied cities. It is not the same as V-E Day, which commemorated the end of the European war in May 1945.