Retired Vice Jerome King Jr., 88, the commander of U.S. naval forces in Vietnam who helped wind down the military branch’s involvement in the Vietnam War, died Friday at Huntington Hospital in Pasadena, Calif. He had chronic obstructive pulmonary disease and pneumonia.

King held demanding assignments at sea and in the front offices of the Navy hierarchy. His most crucial mentor was Thomas Moorer, who became chief of naval operations and chairman of the Joint Chiefs of Staff.

Moorer had taken note of King’s skill and helped his protege win several important jobs. The most public task was succeeding then-Vice Elmo Zumwalt Jr. as commander of naval forces in Vietnam.

Reporting to Saigon in 1970, King continued work started by Zumwalt overseeing the transfer of the Navy’s small coastal and river combat boats to the South Vietnamese. This assignment was part of the U.S. strategy called “Vietnamization,” in which the South Vietnamese took over more responsibility for military operations.

“Vietnamization became frustrating to King because it wasn’t the same desire to victory that had existed before,” said historian Paul Stillwell, who conducted an oral history with King.

“He presided over the diminishment of American capability there,” Stillwell said, “and was not always confident of the South Vietnamese ability or willingness to take over the equipment and the roles” of the U.S. Navy operating in rivers and canals.

After an 11-month tenure in Saigon, King was deputy chief of naval operations for surface warfare. From 1972 to 1974, when he retired from active duty, he was a key aide to Moorer, who was then serving as chairman of the Joint Chiefs of Staff.

Jerome Henry King Jr. was a native of Youngstown, Ohio, and a 1941 engineering graduate of Yale University, where he was in the Navy ROTC program.

He received a master’s degree in nuclear physics from the Massachusetts Institute of Technology in 1951 and became an authority on the effects of nuclear weapons.

His military decorations included three Distinguished Service Medals, two awards of the Legion of Merit, the Bronze Star with Combat V and two awards of the Navy Commendation Medal.

He spent his retirement in Southern California and was a resident of Palos Verdes Estates.

His marriage to Jane Bellows King ended in divorce.