After shakedown off Bermuda and further training at Norfolk and Casco Bay, Maine, Mansfield steamed via the Panama Canal for the West Coast, arriving San Diego 10 September 1944.

From 17 to 23 February, TG 58.1 lent fighter support for the Iwo Jima assault, then steamed at full speed back to the Tokyo area for bombing runs on Nagoya and Kobe.

As heavy weather set in, the task group retired southward, pounding enemy shore installations on Okinawa while en route to Ulithi for replenishment.

Three weeks before VJ Day, Mansfield, with eight destroyers of DesRon 61, conducted a daring high‑speed torpedo run into Nojima Saki, sinking or damaging four enemy ships.

After witnessing the formal Japanese surrender ceremony (alongside the USS Missouri) in September in Tokyo Bay, Mansfield returned to the West Coast.

During the postwar years, the combat veterans trained reservists from the West Coast and made annual cruises to WestPac as part of the Destroyer Force, Pacific Fleet.

Two weeks after Inchon, Mansfield, while searching for a downed Air Force B‑26, struck a mine which severed the bow below the main deck and seriously injured 27 crewmembers.

Receiving a stub bow at Subic Bay, she steamed to Naval Shipyard, Bremerton, Washington for repairs; rejoining the U.N. Fleet off South Korea late in 1951 for gunfire support, escort, and shore bombardment duty.

In June 1966, Mansfield was once again assigned Yokosuka Naval Base as her homeport, after which her deployment schedule repeatedly took her back to the South China Sea for operations off the coast of Vietnam.

Excluding 2 weeks in September with TF 130 as an alternate recovery ship for Gemini XI and 2 weeks in late November as station ship at Hong Kong, she spent the remainder of 1966 off the Vietnamese coast in roles which ranged from blockade patrol in the I Corps area and the interdiction of junk and sampan traffic from the north into South Vietnam, to gunfire support south of Saigon.