Having survived the bloody Battle of New Orleans and the loss of his ship, Captain Sam Bowater is given new orders - to take command of an ironclad warship being built in Memphis, Tennessee. Bowater and his men are taken up river by 'Mississippi' Mike Sullivan, one of the wild, undisciplined captains of the River Defence Squadron, only to find, on their arrival, that their ship is not even half-built and the enemy is closing in fast. Against his better judgment, Bowater joins forces with the Sullivan on board his river gunship. Outnumbered and outgunned, the Confederates once again fling themselves bravely at the overwhelming power of the Yankee invaders. The deadly fight along the Mississippi ends at last in the massive naval battle of Memphis, as the Confederates attempt to hold back the Northern advance.