As captain of a gun on board the U.S.S. Richmond during action against rebel forts and gunboats and with the ram Tennessee in Mobile Bay, 5 August 1864. Despite damage to his ship and the loss of several men on board as enemy fire raked her decks, Deakin fought his gun with skill and courage throughout a furious two-hour battle which resulted in the surrender of the rebel ram Tennessee and in the damaging and destruction of batteries at Fort Morgan. He also participated in the actions at Forts Jackson and St. Philip.