During this period, Saint Paul also bombarded industrial targets: first on textile mills at Hamamatsu during the night of 29 July, and then on 9 August at iron and steel works in Kamaishi, firing the war's last hostile salvo from a major ship.

When hostilities broke out in the Korean War in June 1950, Saint Paul was conducting a midshipman training cruise from San Francisco, California, to Pearl Harbor.

She disembarked the future naval officers and proceeded late in July to the western Pacific where she joined Task Group 77.3 (TG 77.3) on patrol in the Formosa Strait.

She then moved north into the Sea of Japan to join TF 77, and commenced combat operations off the northeast coast of Korea on 9 November.

As the Chinese Communists began massive attacks late in November, United Nations forces commenced a general withdrawal to consolidate and hold south of the 38th parallel.

Saint Paul provided close support for the Republic of Korea I Corps on their east flank as they withdrew from Hapsu, and along the coast, as they retired from Chongjin.

On 7 April, in TF 74, with Wallace L. Lind, Massey, Fort Marion and Begor, Saint Paul helped to carry out raids on rail lines and tunnels utilizing 250 commandos of the 41st Independent Royal Marines.

These highly successful destructive raids slowed down the enemy's resupply efforts, forcing the Communists to attempt to repair or rebuild the rail facilities by night while hiding the work crews and locomotives in tunnels by day.

Saint Paul returned to the United States for yard work at San Francisco, California, from June to September, then conducted underway training before sailing on 5 November for Korea.

[4] Before returning to Japan for repairs, however, Saint Paul carried out gunstrikes on railroad targets near Songjin, during which she captured nine North Koreans from a small boat.

This overhaul period included removing the forward 5" gun turret and adding a large deck house between the funnels to accommodate enhanced flagship facilities.

She departed that port on 6 November; and, after refresher training at San Diego, California, arrived at Yokosuka, Japan, on 29 September to relieve Rochester as 7th Fleet flagship.

She spent most of her time in Keelung or Kaohsiung, Taiwan, with periods of training in the Philippines and port calls at Buckner Bay, Hong Kong, Manila, and Sasebo.

Saint Paul arrived at Long Beach, California, on 21 May and subsequently cruised along the West Coast, as far north as Seattle, Washington, until she sailed once more on 3 February 1958 for the Far East.

She repeated her past WestPac deployments with duties as flagship, and exercises in the Philippines, before returning to Long Beach on 25 August for maintenance and upkeep.

Sailing from Long Beach, California, on 4 May 1959, Saint Paul became the first major United States Navy ship to be homeported in the Far East since before World War II.

The ship was never mentioned by her actual name (her large hull number on the bow was painted over), but was simply referred to as "Old Swayback" and was supposedly commanded by Wayne's character as a captain, served as his flagship as a rear admiral, and was later sunk during a crucial battle with the Japanese.

From that year, she made five successful deployments with the 7th Fleet in operations off North and South Vietnam, providing gunfire support to allied troops.

Reminiscent of her Korean operations, Saint Paul was hit on 1 September 1967 by a shell which struck her starboard bow, near the water line.