On August 8, 1860, he captured the slaver Erie, commanded by Nathaniel Gordon, off the mouth of the Congo River and forced that ship to unload its captive cargo at Monrovia, Liberia.

[6] Promoted to captain effective July 16, 1862,[2] he took part in the Battle of Port Royal under Admiral Samuel Francis Du Pont.

Although not part of Du Pont's plan, he placed Mohican in position to secure an enfilading fire on Fort Walker on Hilton Head Island, South Carolina, and materially assisted in silencing the batteries of the enemy.

[8] In 1863 he was promoted to commodore; and commanded the 4th Division of Admiral David Dixon Porter's fleet at the first and second battles of Fort Fisher, North Carolina, in December 1864 and January 1865.

In the report of the latter action he was specially commended for the support rendered the commander-in-chief, and for the good discipline and accurate firing of his ship, the Susquehanna.