The Battalion was relieved from assignment to the Second U.S. Army at Fort Knox, Kentucky and departed on Permanent Change of Station (PCS) orders to USARPAC (Classified).   The units departed Fort Knox at 2330 hours on 15 July 1965 to Port of Call - Oakland, California.   They arrived at Oakland, California at 0700 hours, 16 July 1965; boarded the USNS Hugh J. Gaffey at 1100 hours and departed Oakland, California at 1400 hours on 16 July 1965.

    The USNS Hugh J. Gaffey arrived at Honolulu, Hawaii at 0600 hours on 21 July 1965 and departed at 1000 hours on 22 July 1965.   They crossed the International Date Line on 26 July 1965.   They arrived at Yokohama, Japan at 1000 hours on 31 July 1965.   The next few day was a "milk run" of the Far East.   The USNS departed Yokohama, Japan at 1100 hours on 1 August 1965.   They arrived in Okinawa at 0830 hours and departed at 1200 hours on 6 August 1965.   On 8 August 1965, they arrived at Manila, Philippines at 1400 hours, departed at 1600 hours and arrived at Subic Bay, Philippines at 2000 hours.   They departed Subic Bay, Philippines at 1700 hours on 9 August 1965.

    On 10 August 1965, they were back on the USNS Hugh J. Gaffey and headed for Bangkok, Thailand.   With just a couple more stops to make in South Vietnam.   On 11 August 1965, they arrived at Cam Rahn Bay, Vietnam at 0700 hours and departed at 1800 hours.   On 12 August 1965, they arrived in Saigon, Vietnam (Vong Tau Bay) at 0700 hours and departed at 1200 hours.

    The 538th Engineer Battalion debarked the USNS Hugh J. Gaffey at 0700 hours on 14 August 1965.   They boarded LST's and arrived in Bangkok at 1200 hours, only to be reboarded on buses.   The buses arrived at Camp Friendship at 1700 hours on 14 August 1965.   The next few weeks were spent sending troops TDY to Bangkok to convoy the vehicles and equipment back to Camp Friendship in Korat, Thailand.

    On 14 October 1965, Headquarters and Headquarters Company (HHC,) 538th Engineer Battalion departed Camp Friendship at 0900 hours and arrived at Camp Essayons at 1015 hours.   Camp Essayons (at Pho Dang) was the base camp for HHC, A & B Companies, 538th Engr Bn.   C Company, 538th was relocated to Camp Sungwien up in the mountains.   D Company, 538th Engr Bn set up at Sattahip, to be "Camp Samae San," next to the U-Tapao Royal Thai Air Force Base (RTAFB.)

    On the 4th of November 1965,   the 538th Engineer Battalion was released from assignment to HQ, 9th Logistical Command (B) and reassigned to HQ, 44th Engineer Group (Construction) at Korat, Thailand.