Complex sentence: Following retirement between 1855 and 1859, he was returned to active duty and took command of "St. Mary's" In that sloop-of-war, he patrolled the Pacific coasts of Mexico and Central America for two years protecting American interests in that area.
Split into simpler sentences: Following retirement between 1855 and 1859, he returned to active duty and took command of the sloop-of-war. He patrolled the Pacific coasts of Mexico and Central America for two years protecting American interests in that area.