In early June, Union turned in her 5-inch stern gun and her 20 millimeter mounts to the Naval Repair Facility, San Diego. In July, she participated in Operation "Workhorse," a local landing exercise. On 23 August 1957, Union got underway for WestPac via Pearl Harbor. She arrived at Yokosuka, Japan, on 12 September and underwent restricted availability. Union then visited Kure, Nagoya, and Chigasaki Beach before returning to Yokosuka to pick up Marine Corps cargo for Naha, Okinawa. On 4 November, she sailed for Subic Bay, Philippines. Union spent the remainder of the year in cargo-carrying tasks which took her to Taiwan, the Philippines, Hong Kong, and Okinawa. Christmas and New Year's Day were spent in Subic Bay, Philippines. The year 1958 began with a week-long visit to Hong Kong, after which she proceeded to Yokosuka. On 5 February, Union departed Yokosuka for Okinawa to prepare for Operation "Strongback," a major 7th Fleet amphibious assault exercise at Dingalen Bay, Luzon, Philippines, in which destroyers, cruisers, and carriers took part in screening, gunfire, and air support tasks. D-day was 1 March, and Union returned to San Diego, via Pearl Harbor, on 2 April. April, May, and June 1958 were occupied with leave, upkeep, and local operations in the San Diego area. Union underwent a material inspection during July, and a resupply expedition to the Pribilof Islands scheduled for August was cancelled due to the Lebanon crisis which broke in early July. During September, the ship took part in "Phiblex 2–59," a full-scale landing exercise for the 1st Marine Division at Camp Pendleton. After spending October in the San Diego area, Union sailed on 10 November for San Francisco and another regular yard overhaul. After off-loading cargo and ammunition, she arrived at the Mare Island Naval Shipyard for overhaul which lasted from 17 November 1958 to 16 January 1959. Union returned to San Diego on 25 January. Shortly thereafter, she underwent refresher training, followed by amphibious training commencing on 17 March which completed her "working up." On 16 April, Union sailed for WestPac. On 22 April, she was detached and proceeded independently to Guam, thence to Subic Bay, Philippines. Throughout June, Union remained in the vicinity of Okinawa. She participated in Exercise "Reconnex 1–60" off Irimote Jima, Japan, from 20 to 28 June. On 10 July 1959, Union and embarked the 3rd Anti-Tank Battalion and sailed for Numazu, Japan, to commence the