Complex sentence: Mr. Packard entered the United States Navy upon U.S. involvement in World War I, receiving ground school training at the Massachusetts Institute of Technology, and later was assigned to flying duty at Pensacola, Florida, achieving the rank of ensign and serving throughout the war period.
Split into simpler sentences: Mr. Packard entered the United States Navy upon U.S. involvement in World War I, receiving ground school training at the Massachusetts Institute of Technology. He was later assigned to flying duty at Pensacola, Florida achieving the rank of ensign and serving throughout the war period.