Following shakedown and training out of San Pedro, California, YDG-9 continued operations on the west coast, first for the 11th Naval District and then as a unit of ServRon 8. Later assigned to SevRon 6 to service, in close proximity, the striking forces as they moved closer to Japan, she established and operated degaussing ranges and provided facilities for inspection, calibration, and adjustment of shipboard degaussing equipment in forward areas, primarily for minesweepers. After World War II ended, she operated with mine groups at Okinawa and, after 29 January 1946 at Sasebo, Japan as those groups cleared the waters to allow safe passage to both military and merchant shipping.