Born in 1837 in New York City, Deakin was living in Philadelphia when he joined the Navy. He served during the Civil War as a boatswain's mate and gun captain on the . In April 1862, he took part in the Battle of Forts Jackson and St. Philip in Louisiana. At the Battle of Mobile Bay on August 5, 1864, he "fought his gun with skill and courage" despite heavy fire. For this action, he was awarded the Medal of Honor four months later, on December 31, 1864.