On board the USS Richmond in action at Mobile Bay on 5 August 1864. Cool and vigilant at his station throughout the prolonged action, Cronin watched for signals and skillfully steered the ship as she trained her guns on Fort Morgan and on ships of the Confederacy despite extremely heavy return fire. He participated in the actions at Forts Jackson and St. Philip, with the Chalmette batteries, at the surrender of New Orleans, and in the attacks on batteries below Vicksburg.