Complex sentence: When he was 19, his father suggested he enlist in the Navy so he could avoid ground combat; however, the Navy chose him to become a Pharmacist's Mate and he was eventually assigned to the United States Marine Corps.
Split into simpler sentences: When he was 19, his father suggested he enlist in the Navy so he could avoid ground combat. However, the Navy chose him to become a Pharmacist's Mate and he was eventually assigned to the United States Marine Corps.