Operation Coronado II

Operation Coronado II was the second of eleven in the Operation Coronado series conducted by the American Mobile Riverine Force in conjunction with various units of the Army of the Republic of Vietnam in late July 1967 in an attempt to shut down Vietcong strongholds in the Mekong Delta. Three battalions of American troops, along with two South Vietnamese battalions, backed by helicopters and watercraft swept the area and waterways surrounding My Tho in search of communist forces. Two battalions of communists were encountered and many captured, although both sides suffered numerous casualties. The anti-communist forces also cordoned off the area to search water traffic for communist supplies or suspects. The Americans credited the 3d Vietnam Marine Battalion for the success of the operation.

Start of operation
The Mobile Riverine Force ended Operation Coronado I in Long An Province because of intelligence indicating communist buildup west of My Tho in Dinh Tuong Province. The force received word on 25 July that the Mobile Riverine Base would move on 27 July from the confluence of the Soi Rap and Vam Co Rivers to the vicinity of Dong Tam. During the afternoon of 25 July ground forces were picked up by assault craft and returned to the Mobile Riverine Base. At 0200 on 27 July riverine assault craft began leaving the base for minesweeping and patrol stations along the route to Dong Tam. At 0550 the last ship of was proceeding south on the Soi Rap River. Because of the slow speed of the towed APL moving against the tide the journey took almost 12 hours, but did not delay the commencement of the new operation in Dinh Tuong Province on 28 July. In just over 48 hours the Mobile Riverine Force was able to relocate a base supporting 3,900 men a distance of 96 km and to shift its area of operations a total of 136 km to the area west of Dong Tam.

The Mobile Riverine Force was about to join the largest force with which it would co-operate in a single operation in its Vietnam experience. Intelligence indicated that a Viet Cong force of several battalions threatened My Tho and Dong Tam; the plan was to attack simultaneously three of the four Vietcong base areas in Dinh Tuong Province from which a communist attack might be staged.

On 27 July the 7th ARVN Division initiated operations designed to sweep for Viet Cong from east to west, north of Highway 4. The search would cover the territory around the Ap Bac base area and in the eastern portion of the Vietcong Base Area 470. On 28 July the Mobile Riverine Force would move into the Cam Son base area; on 29 July one or more battalions of the Republic of Vietnam Marine Corps would move into the Ban Long base area. The US 9th Division was to place the 5th Battalion, 60th Infantry (Mechanized), under the operational control of the 2d Brigade for the Cam Son operation, and was to hold the 3d Battalion, 39th Infantry, on call at that battalion's Long An base camp. The 1st Brigade, US 25th Division, was to arrive at Dong Tam on 28 July for commitment under the operational control of the 9th US Division. The 7th ARVN Division was given the 44th Ranger Battalion by the commander of South Vietnam's IV Corps for insertion by helicopter into the northwestern portion of Cam Son on 28 July. The US Navy Task Force 116 (Game Warden) was to patrol the My Tho River from My Tho to Sa Dec with 30 river patrol boats. To facilitate command and control, the US 9th Division moved a forward command post to Dong Tam for the operation.

28 July
The Mobile Riverine Force operation in Cam Son began during the evening of 28 July with the movement of the 5th Battalion, 60th Infantry (Mechanized), from its Long An base camp along Highway 4 to the town of Cai Lay. A battalion command post was established there as the maneuver companies continued south into the Cam Son area. As the mechanized battalion moved into the area of operations from the northeast, the 3d and 4th Battalions of the 47th Infantry moved by assault craft into the waterways in the southern portion of Cam Son.

Troop D, 3d Squadron, 5th US Cavalry Regiment, apart from its aerial rifle platoon, was operating with the Mobile Riverine Force for the first time. The troop had a reconnaissance mission covering eastern Cam Son and western Ban Long on the brigade's flank. One rifle company of the 3d Battalion, 60th Infantry, was on call to the 2d Brigade for airmobile employment from Dong Tam.

Two assault helicopter companies were available to the 2d US Brigade from II Field Force. At 0800 on 28 July they conducted feint landings at two landing zones just north of known communist fortifications in northern Cam Son to delay Vietcong movement north until both the 5th Battalion, 60th US Infantry, and the 44th Vietnamese Ranger Battalion could move into blocking positions near the feint landing zones.

On 28 July troops of the 7th ARVN Division north of Highway 4 received a sporadic Vietcong fire and the Mobile Riverine Force encountered a few communist in Cam Son. Troop D detected a squad of communists in the Ban Long area and killed five of them with gunship fire. Throughout the late morning on 29 July both the 3d and 4th Battalions, 47th US Infantry, discovered widely dispersed small groups of Vietcong. From their movements it was deduced that these groups were trying to retreat north into a fortified area. As the 3d Battalion moved companies into this area from the north and south on the east bank of the Rach Ba Rai, the communists resisted. Between the hours of 1700 and 1900, Company C of the 3d Battalion pressed north; small enemy groups moving northeast delayed the company's advance. During these two hours an ATC was hit by B-40 rockets and 57-mm. recoilless rifle fire; 25 American troops were wounded by fragments. The 5th Battalion, 60th US Infantry fired upon individuals and small groups of Vietcong during the late afternoon and evening. None of the Mobile Riverine Force units were able to determine the communist position and by 1930 contact was lost. Most of the Vietcong dead were found when the anti-communist infantry moved into areas that had been attacked by artillery and helicopter gunships.

29 July
By the night of 29 July, the fact that the 7th ARVN Division north of Highway 4 had found few Vietcong and that the communists in central Cam Son had evaded major battle prompted General O'Connor, commander of the US 9th Division; and Colonel Lan, commander the South Vietnamese marine unit, to consider the probability that the communists were in the Ban Long area. Although the Mobile Riverine Force intelligence gathered in central Cam Son was far from conclusive, the highly evasive communist tactics when encountered by the anti-communist forces was considered to be an indication that those Vietcong encountered might be protecting the movement of larger units into Ban Long. This was in keeping with the pattern of movement in southern Dinh Tuong Province, and while no communists were detected in Ban Long by D Troop on 29 July, a Vietcong squad had been attacked there by gunships on 28 July.

At approximately 2000 on 29 July Colonel Lan selected a landing zone for his 3d Republic of Vietnam Marine Battalion to begin landing by helicopter in Ban Long the next day. The area selected by Colonel Lan as a likely enemy position was near where D Troop had discovered the communists on 28 July.

30 July
When it landed on 30 July, the 3d South Vietnamese Marine Corps Battalion met heavy resistance. They immediately attacked the communists, who were in a wooded area north of the landing zone. More marines were airlifted into the landing zone under continuous communist fire. For five hours the marines attacked prepared Vietcong defensive positions, who fired light and heavy machine guns and mortars. In contrast, the marines relied on helicopter gunships and artillery. The 3d Marine Battalion fought the enemy throughout the afternoon, capturing some communist equipment.

Noting the long east-west belt of trees that could provide concealment for the communists, O'Connor employed the 1st Brigade, 25th US Division, east of the marines' location to block any communist movement towards the east. In mid-afternoon General O'Connor directed Colonel Fulton, commanding officer of the 2d Brigade, to assist the 3d South Vietnamese Marine Battalion in evacuating casualties and preparing for an attack against the Vietcong. Colonel Fulton directed Lieutenant Colonel Bruce E. Wallace, commander of the 3d Battalion, 47th US Infantry, to establish a blocking position west of the battle area, facing east, which was accomplished by 2000. The 4th Battalion, 47th Infantry, deployed in the field for three days, returned to the Mobile Riverine Base with instructions to be prepared to deploy early on 31 July. The 5th Battalion, 60th US Infantry, was detached to 9th US Division at 1230.

During the action on 29 July, several assault boats were hit with small arms, rocket, and recoilless rifle fire. No monitors suffered major structural damage. Hits and minor damage were received by five craft, but the boats were able to remain in operation. At approximately 2030 on 30 July, Colonel Lan requested illumination for a night attack against communist positions. The subsequent attack by the 3d Vietnam Marine Corps Battalion silenced several 12.7-mm. Vietcong machine guns. The attack was stopped by the South Vietnamese Marine commander because his own losses were also heavy. Illumination was maintained during the night; at approximately 0430, 31 July, the Vietcong counterattacked to the east, with heavy losses to both sides.

31 July
Later in the morning of 31 July, the 5th Battalion, 60th US Infantry Regiment, was again placed under the leadership of Colonel Fulton. At 0835, the battalion went to the assistance of the 1st ARVN Cavalry Squadron and the 44th Vietnamese Ranger Battalion, which had met the communists while moving to assist the 3d South Vietnamese Marine Battalion. By 0825 the 5th Battalion, 60th Infantry occupied a blocking position northeast of the 3d Battalion, 47th Infantry, where it remained for the day. During the morning of 31 July, the 3d Battalion, 39th Infantry Regiment was placed under the operational control of Colonel Fulton, bringing the Mobile Riverine Force to four battalions and Troop D, 3d Squadron, 5th Cavalry. The 3d Battalion, 39th Infantry landed south of Vinh Kim and searched west.

Reports from the 44th Ranger Battalion and 3d Marine Battalion indicated that the communist forces, identified as the 263d Vietcong Main Force Battalion, had dispersed during the pre-dawn counterattack and were moving south. Airborne reconnaissance by the 3d Battalion, 39th Infantry, revealed movement south towards the village of Ap Binh Thoi.

Colonel Fulton directed the 3d Battalion, 39th Infantry, to conduct reconnaissance using helicopters southeast of the battle area and moving west to Ap Binh Thoi. He directed Colonel Wallace to move his battalion southeast and to search the area as he moved on Ap Binh Thoi. This search was initiated in mid-morning and by 1700 both American battalions were on the outskirts of Ap Binh Thoi. During that time Vietcong were observed moving into the village in groups of 25–30.

The 4th Battalion, 47th Infantry and elements of Vietnamese military police company landed by ATC and entered Ap Binh Thoi. One American company moved out to search northwest of the town while the rest of the battalion assisted the Vietnamese police in apprehending and interrogating people suspected of being communists. Several of the prisoners reported they were from the 263d Main Force Vietcong Battalion and elements of the 514th Local Force Vietcong Battalion. The prisoners were classified as communists when they confessed to having hidden their weapons as they left the battle area before sunrise. Company C, 4th Battalion, 47th Infantry, captured four men northwest of Ap Binh Thoi, all of them members of the 263d Main Force Battalion including the battalion's deputy commander. Of the more than 400 suspects detained by the Vietnamese police, 83 were from the 263d Main Force Battalion. The cordon around Ap Binh Thoi was completed by nightfall on 31 July, and no more Vietcong were sighted.

The four-day operation caused heavy losses to the 263d Vietcong battalion. The Americans said that this was "primarily because of the outstanding performance of the 3d Vietnam Marine Battalion...[who] destroyed major fortifications in the Cam Son base area, probably thwarted planned enemy operations against Dong Tam, and eased the pressure on Highway 4."

After this was done intelligence sources reported that the communists had attempted to organize boats for a crossing of the My Tho River into Kien Hoa Province but were blocked by the cordon at Ap Binh Thoi and the river patrols. During the five-day operation on the My Tho River, more than 50 patrol craft were employed; 283 Vietnamese watercraft were stopped and searched by US naval craft and the Mobile Riverine Force in the most ambitious attempt to control river traffic during 1967.