Commissioned as an ensign in the Navy upon graduation from the United States Naval Academy in 1916, he served in the battleship USS Pennsylvania (BB-38) for more than four years, including the U.S. participation in World War I.

In 1923, after receiving a graduate education in engineering, he began two years as Aide and Flag Lieutenant to Commander, Yangtze Patrol.

For several months after the United States entered World War II in December, he helped to plan and execute combat operations against Japan.

He commanded the heavy cruiser USS Louisville (CA-28) from September 1942 to June 1943 during which he was active in the Aleutians and South Pacific war theatres.

After an important war plans tour in Washington, DC, Rear Admiral Joy became commander of a cruiser division, leading it through nearly a year and a half of intense combat service against the Japanese Navy.

Vice Admiral Joy held that position until mid-1952, directing much of the Navy's effort during the first two years of the Korean War.