Complex sentence: In September 1942, Pharmacist's Mate Wheeler B. Lipes performed the first major surgery aboard a submarine when a shipmate showing symptoms of acute appendicitis required an emergency operation in order to survive.
Split into simpler sentences: In September 1942, Pharmacist's Mate Wheeler B. Lipes performed the first major surgery aboard a submarine. A shipmate with acute appendicitis required an emergency operation in order to survive.