Served on board the U.S.S. Fort Hindman during the engagement near Harrisonburg, La., 2 March 1864. Following a shellburst at one of the guns which started a fire at the cartridge tie, Duncan immediately seized the burning cartridge, took it from the gun, and threw it overboard, despite the immediate danger to himself. Carrying out his duties through the entire engagement, Duncan served courageously during this action in which the Fort Hindman was raked severely with shot and shell from the enemy guns.