to Da Nang, South Vietnam, where she back-loaded BLT 3/3 (Battalion Landing Team, 3rd Battalion, 3rd Marines) and transported the marines to Okinawa for a recreation and retraining cycle. Union then proceeded to Cam Ranh Bay, South Vietnam, where, on 15 September, elements of the Republic of Korea Marines were loaded for transportation to Chu Lai. When this offload had been completed, boiler troubles forced Union into an availability at Subic Bay from 27 September through 7 October. With all repairs completed, Union commenced a lengthy period of support operations for Commander, Military Assistance Command, Vietnam, which extended to 21 November. The ship arrived at Okinawa on 26 November and, after a few days for liberty and replenishment, loaded elements of BLT 1st Battalion, 9th Marines (BLT 1/9). She sailed for Subic Bay, Philippines, on 3 December. On 14 December, Bravo Company from BLT 1/9 conducted wet-net training on the "Union" to practice amphibious doctrine in preparation for Operation Deckhouse V. After her detachment from this duty, Union set course for Sasebo, looking forward to a holiday upkeep period which lasted through the 27th. As the year closed, Union was once again at Okinawa loading BLT 4th Battalion, 4th Marines. On the final day of 1966, a practice turnaway landing was conducted at Chin Wan in preparation for actual movement across the beach that would follow on New Year's Day. The first day of 1967 found Union in the last phase of her WestPac tour. After landing craft training operations in the Okinawa area, Union departed Okinawa en route to Da Nang, Vietnam. After off-loading and back-loading Marine vehicles, the ship returned to Okinawa on 14 January. An upkeep period at Sasebo, Japan, began on 17 January and was followed by rest and recreation at Keelung, Taiwan, and Kobe, Japan. On 15 February, Union set course for Yokosuka, Japan, spending 10 days in port there and then departing for San Diego. Union entered San Diego Bay on 15 March 1967, completing her 15th WestPac cruise. After a month-long leave period, preparations began for Operation "Alligator Hide," an amphibious assault at Coronado Roads, California. Following the operation, Union spent 13 days in port and, on 15 May, conducted individual ship exercises. On 29 May 1967, Union suddenly received orders to perform duties as a reconnaissance ship, trailing the Russian trawler Peleng, which had been operating off the coast of southern California