On board the U.S.S. Brooklyn during action against rebel forts and gunboats and with the ram Tennessee, in Mobile Bay, 5 August 1864. Despite severe damage to his ship and the loss of several men on board as enemy fire raked her decks from stem to stern, Cooper fought his gun with skill and courage throughout the furious battle which resulted in the surrender of the prize rebel ram Tennessee and in the damaging and destruction of batteries at Fort Morgan.
Served as quartermaster on Acting Rear Admiral Thatcher’s staff. During the terrific fire at Mobile, on 26 April 1865, at the risk of being blown to pieces by exploding shells, Cooper advanced through the burning locality, rescued a wounded man from certain death, and bore him on his back to a place of safety.
G.O. No.: 62, 29 June 1865.