Complex sentence: At the outbreak of the American Civil War, however, he pled his case to United States Secretary of the Navy Gideon Welles himself, was reinstated and went on to acquire a distinguished record, frequently volunteering for the most hazardous missions.
Split into simpler sentences: At the outbreak of the American Civil War, however, he pled his case directly to United States Secretary of the Navy Gideon Welles and was reinstated. He then went on to acquire a distinguished record, frequently volunteering for the most hazardous missions.