It was composed in 1922 by USC dental student, Milo Sweet, with lyrics by Sweet and Glen Grant, for a student spirit competition.
During World War II, the song was used to inspire combat-bound troops in the Aleutians Campaign.
According to legend, it was played off the deck of a transport carrying American soldiers onto the beach of a Japanese-held island; the troops let out a roar when they heard the song and eventually captured the island.
[1] The term, "Fight On", is also used as a battle cry for USC fans.
Like many other college fight songs, "Fight On" is used by many high schools throughout the United States, though often with modified lyrics.