Her next Pacific deployment came after the invasion of South Korea by the Communists in June 1950. "Marsh" arrived at Yokosuka, Japan on 7 September, and departed on the 14th for Pusan, where she supplied power to the city for two weeks. On 9 October, she entered Inchon Harbor, and remained as support for that area's defense until the end of the month. She supplied power at Masan, a seaport on Chosen Strait, for a month starting on 9 November, then returned to Pusan where she remained as a ship-to-shore power unit for the remainder of her tour.