In the closing days of April, the JGS ordered Lieutenant Colonel Khang to form two infantry battalions and an artillery clement into a provisional brigade for immediate assignment to II Corps. There the Vietnamese Marines were to join elements of the 2d and 25th ARVN Divisions for a multi-regiment thrust into the rugged mountains just south of the I Corps-II Corps border. Code named BACH PHUONG XI, this offensive was to penetrate the Do Xa, a Viet Cong base area never before entered by government forces. Centered in that portion of the Annamite Mountains where the borders of Quang Tin, Quang Ngai, and Kontum Provinces converged, the Do Xa had been under Communist control since the early stages of the French-Indochina War. In this remote, inaccessible mountainous zone the Viet Cong reportedly had built-up extensive staging areas and training camps. Prisoner interrogations obtained throughout the early 1960s revealed that many North Vietnamese soldiers entering the South's northern provinces had infiltrated the Do Xa before moving into the densely populated coastal lowlands of Quang Tin and Quang Ngai provinces. Additionally, the area was thought to contain the Communist military headquarters for Military Region 5 (MR-5).

After alerting his 2d and 4th Battalions, a pack howitzer battery, a reconnaissance platoon, and a headquarters element, Khang flew with Lieutenant Colonel Moody to Pleiku for planning conferences with Major General Nguyen Khanh and his II Corps staff. The concept of BACH PHOUNG XI, Khang and Moody learned, called for U.S. Marine and Army helicopters to lift ARVN infantry and artillery elements into positions which would form a loose ring around the suspected center of the Do Xa base area. The ARVN units would then begin contracting this ring in stages, whereupon the provisional Marine brigade would be helilifted into its center, the heart of the Do Xa, to search for Communist camps. To control the entire operation General Khanh would establish a corps headquarters forward at Plateau Gi, a Montagnard village located on the southern edge of the operations area, about 25 miles northeast of Kontum.

On 1 May, U.S. Air Force C-123 transports airlifted Khang and the 2,000-man provisional Marine brigade from the capital to Quang Ngai. Both Lieutenant Colonel Moody and Major Croft, the Assistant Senior Marine Advisor and artillery advisor, accompanied the Marine force. The next day an ARVN truck convoy transported the Marines from Quang Ngai some 40 miles north to Tam Ky, the roadside town which served as the capital of Quang Tin Province. The 2d Battalion, advised by Captain Taylor, dismounted from the trucks and assembled at Tam Ky airstrip while the remainder of the convoy turned west onto a narrow dirt road which curved through the foothills and deep into the jungle-covered Annamite Chain. Meanwhile, Army H-21s from Pleiku landed at Tam Ky, loaded assault elements of the 2d Battalion, and began helilifting them into a stream-side landing zone some 30 miles southwest of the provincial capital. The convoy carrying the balance of the Marine force continued its southwest motor march until it reached the small ARVN-held town of Tra My. There, some 24 miles southwest of Tam Ky, Khang established his command post in a school house adjacent to a crude little dirt airstrip. The 75mm pack howitzer battery, advised by Major Croft, set up its weapons nearby while the reconnaissance platoon and elements of the 4th Battalion, advised by Captain Christensen, established security. When these units were in place U.S. Marine UH-34Ds from Da Nang lifted a TAFDS [Tactical Airfield Fuel Dispensing System] fuel bladder and pump to the airfield. Once the helilift of the 2d Battalion was completed, the Army H-21s, refueling from the TAFDS bladder, began lifting the 4th Battalion into the 2d Battalion's landing zone, which was located several miles south of Tra My. With the initial movement into the operations area accomplished and the brigade command post functioning, the two infantry battalions began combing a deep valley and the adjacent mountains for Communist base camps.

After several days Khang's Marines located one rather complete camp but encountered no resistance upon entering the position. Once again the occupants, probably forewarned by the initial movement of the ARVN units into the area, had withdrawn ahead of the Marines. The only people found in the camp were a North Vietnamese doctor and nurse. A subsequent search of the bamboo huts and the underlying tunnel complex did produce a supply cache. The Vietnamese Marines discovered several rifles, six typewriters, three sewing machines, a radio, 44 maps, a French artillery computing board, and scores of flashlight batteries.

ARVN and Marine operations in the area during the next two weeks failed to locate any large Viet Cong elements. For the most part the Marines busied themselves by destroying a few abandoned camps and some cultivated crops. ARVN units operating around the Marines reported scattered action as they engaged small groups of Viet Cong attempting to escape from the center of the Do Xa. BACH PHOUNG XI concluded in mid-May when U.S. Marine UH-34Ds lifted the VNMC battalions back to Tra My. From there the Marines returned by convoy to Quang Ngai where they staged for the airlift back to Saigon. The statistics for the Marine portion of the operation revealed that only two Viet Cong soldiers had been killed. Khang's force suffered 36 wounded, most as a result of encounters with booby traps constructed from sharpened bamboo spikes. ARVN forces fared only slightly better, having killed barely a score of Communists. Except for the fact that they had demonstrated their ability to penetrate the most difficult Viet Cong sanctuary, the two-week offensive into the Do Xa base area had little impact on the war effort. From the standpoint of training and experience, however, the operation was beneficial. The Vietnamese Marines and their advisors learned a great deal about construction of landing zones and about directing helicopters, fields in which they had received little previous training.

(From “The Advisory & Combat Assistance Era: 1954-1964”, pp 102-104, Captain Robert H. Whitlow, USMCR)