Chapter III:
(2-24 October 1966)
Operation IRVING illustrates a number of innovations which were used throughout Vietnam. These innovations represented important changes in the tactical, technical, and psychological sides of warfare. The helicopter played an enormous part, not only in lifting troops into combat but also as aerial rocket artillery, in the evacuation of casualties, in logistical support, and in the development of new lightweight equipment. IRVING also demonstrates the use of civic action and psychological warfare in counterinsurgency operations. In addition to being outflanked by vertical envelopment, the enemy was attacked by strategic bombers and by U.S. infantrymen invading his underground hiding places.
During October of 1966, allied military forces combined efforts in three closely co-ordinated operations to destroy the enemy in the central and eastern portions of the Republic of Vietnam's Binh Dinh Province and to uproot the Viet Cong's political structure along the province's populated coastal region. In a period of twenty-two days, the 22d ARVN Division, the Republic of Korea Capital Division, and the U.S. 1st Cavalry Division (Airmobile) were to dominate the battlefield to such an extent that the aggressor had only one alternative to fighting: surrender. The enemy not only suffered heavy personnel losses in decisive combat, but many of his vital logistic and support bases were discovered and destroyed. The victory meant that the central coastal portion of Binh Dinh Province and hundreds of thousands of citizens were returned to the control of the South Vietnamese government. The people of the province were freed from Viet Cong terrorism and extortion for the first time in many years, and the groundwork was laid for a better life. The U.S. 1st Cavalry Division's contribution in this campaign to pacify Binh Dinh Province was Operation IRVING.
IRVING began on 2 October 1966; however, the development of the battlefield started many days before. The enemy had been driven out of his bases in the Kim Son and 506 valleys and channeled toward the sea. In Operation THAYER I in September, strong U.S., South Vietnamese, and Korean attacks from all sides uprooted elements of the 610th North Vietnamese Army Division from their mountain 

sanctuaries, uncovering major medical, arms, supply, and food caches, a regimental hospital, and a large antipersonnel mine and grenade factory. A series of fierce battles forced the enemy into a natural pocket bounded by the Phu Cat Mountains on the south, the coastline on the east, the Nui Mieu Mountains on the north, and National Route 1 on the west, The battle lines for Operation IRVING had been drawn.
The 1st Cavalry Division planned for Operation IRVING in minute detail. The division staff concentrated on intelligence, psychological operations, population control, and civic action projects as well as combat operations. If combat against the enemy was to be successful, the psychological, population control, and civic action aspects had to be effective. In the same pocket with the enemy were some 250,000 civilian residents, plus important rice farming and salt production areas. To avoid noncombatant casualties, population control measures were incorporated into the psychological operations program. Some twelve million leaflets and 150 radio broadcast hours were used during Operation IRVING to help control the civilians. Curfews were established, and at times villagers were requested to stay where they were until more specific instructions were given. Psychological efforts were also geared to appeal to the enemy. For example, substantial rewards were offered for surrendered weapons.
By D-day for Operation IRVING, the Free World Military Assistance forces were in position. Elements of the 1st and 3d Brigades of the 1st Cavalry Division air-assaulted into objectives well inside the IRVING pocket. Simultaneously, the ARVN and Korean elements coordinated attacks in the southern portion of the battle area so that all three schemes of maneuver would complement one another. The 22d ARVN Division launched a ground attack to the northeast with two infantry battalions and two airborne battalions. The Republic of Korea Capital Division attacked northward through the Phu Cat Mountains. On the South China Sea, the ARVN junk fleet and the U.S. Navy sealed escape routes to the sea and provided fire support from the destroyers Hull and Folson and smaller ships.
The 1st Cavalry Division attacked at 0700 hours on the morning of 2 October. Colonel Archie R. Hyle, commander of the 1st Brigade, deployed the 1st Battalion, 8th Cavalry, to gain objective 5060; the 2d Battalion, 8th Cavalry, to secure objective 506A; and the 1st Battalion, 12th Cavalry, to attack objective 506B. The 3d Brigade commander, Colonel Charles D. Daniel, attacked objective 507 using the 1st and 5th Battalions of the 7th Cavalry. The 1st Squadron, 9th Cavalry, under the control of Major General John Norton, the division commander, was assigned its normal reconnaissance mission over the division's area of interest. Decisive combat with the enemy was to occur shortly after the operation began.

Early on the morning of D-day, elements of the 1st Squadron, 9th Cavalry, were conducting reconnaissance operations in the vicinity of Hoa Hoi and observed seven North Vietnamese Army soldiers in the village. Troop A landed its infantry elements in the village area and supported them with armed helicopters. They soon were engaged against a large enemy force that had fortified the village. When advised of the situation at Hoa Hoi, Colonel Hyle called for the 1st Battalion, 12th Cavalry, already airborne en route to another objective. Lieutenant Colonel James T. Root, commander of the 1st Battalion, issued new orders from his command and control helicopter, and the battalion turned to the rescue.
B Company was the first unit of the 1st Battalion to arrive at Hoa Hoi. Under the direction of Captain Frederick F. Mayer, Company B landed 300 meters east of the village and quickly maneuvered to assault the enemy's fortified positions. Although wounded, Captain Mayer directed the unit's drive toward the well-prepared enemy bunker system. While advancing across an open area, the unit came under extremely heavy fire and was momentarily pinned down. Members of the 2d Platoon, Company B, stood up and advanced through the enemy fire. One squad, spearheaded by Private, First Class, Roy Salagar, breached the heavily booby-trapped perimeter trench, and within minutes the enemy force started withdrawing into the village.
At this time A Company air-assaulted into an area southwest of Hoa Hoi. As the 3d Platoon came in contact with the enemy, they also encountered civilian noncombatants in the battle area. First Lieutenant Donald E. Grigg was deploying his platoon to return fire when several old men, women, and children walked between him and the enemy. He raced 150 meters through concentrated fire, picked up two of the small children, and carried them back to his own lines. The other civilians followed him to safety. Lieutenant Grigg's platoon then closed in on the enemy and forced him to withdraw into the village.
While other elements of the 1st Battalion, 12th Cavalry, were being air-assaulted into the battle area, the battalion held its fire on the village. A psychological operations helicopter circled the village with loudspeakers, directing the civilians to move out of the village and into four specific areas outside the perimeter. North Vietnamese Army soldiers were asked to lay down their weapons. During the moratorium, many civilians and soldiers did as they were directed. After one hour, when it was evident that no one else was coming out of the village, the 1st Battalion, 12th Cavalry, began moving in.
Fierce fighting lasted throughout the day as elements of the U.S. battalion assaulted the fortified village. That evening, General Norton reinforced the 1st Battalion, 12th Cavalry, with Companies A and C of the 1st Battalion, 5th Cavalry. Under the control of Colonel Root, the companies made a night air assault on the beaches east of

Hoa Hoi and moved into the encirclement to help contain the enemy during the hours of darkness. North Vietnamese soldiers tried in vain to shoot their way out. Effective artillery support contributed to the containment effort. Earlier in the day, A Battery, 2d Battalion, 19th Artillery, had been positioned by assault support helicopters to back up the 1st Battalion, 12th Cavalry. During the night 883 105-mm. rounds were fired in the effort to contain the enemy. The battlefield was illuminated by a U.S. Air Force AC-47 flareship, by artillery, and by naval guns from the destroyer Ullman. Throughout the night, helicopters provided fire support, brought in supplies, and evacuated casualties.
At dawn, Company C, 1st Battalion, 12th Cavalry, attacked south through the enemy position, while Companies A and B blocked the other side of the village. The enemy defended with great skill; but the strength of the attack, plus the well-co-ordinated combat support, brought the battle of Hoa Hoi to a close. During this 24-hour battle, the 1st Battalion, 12th Cavalry, and supporting units had killed or wounded 233 enemy soldiers, while suffering 3 killed and 29 wounded. In addition, 35 North Vietnamese soldiers were captured, and 15 suspected NVA regulars were detained.
On D-day of the operation a B-52 strike was made on a portion of the Nui Mieu Mountains near objective 506A. The 1st Squadron, 9th Cavalry, conducted a follow-up damage assessment and discovered documents and seven enemy dead, which confirmed the presence of elements of the 2d Viet Cong Regiment. All forces advanced on schedule to reduce the size of the IRVING pocket. The sweep to the sea continued, using helicopter assaults and land movement to destroy the enemy forces. On 4 October a co-ordinated ground attack was made by the 3d Brigade using the 1st and 5th Battalions, 7th Cavalry. The attack was preceded by extensive artillery preparation. Thirty enemy soldiers were killed in the operation. As the sweep operations neared Nuoc Ngot Bay, leaflets and loudspeakers were used to warn civilians that all boats moving on the bay would be sunk. Riot control agents were also used during the operation. The battalions of the 3d Brigade used assault boats brought in by helicopter to sweep the waterways.
On 5 October the 1st Battalion, 12th Cavalry, air-assaulted back to the west into the Soui Ca Valley to exploit a B-52 strike and to surprise enemy units that had escaped the IRVING pocket or had secretly moved into the valley strongholds. In the IRVING battle area, the 1st Cavalry Division continued to search for North Vietnamese units and to uproot the Viet Cong. The 1st Squadron, 9th Cavalry, sighted many small groups of enemy soldiers trying to avoid contact. The cavalrymen fired at them from armed helicopters and often landed infantry elements to engage the enemy. On 9 October, while supporting

PICTURE : CH-54 "FLYING CRANE" Delivering  Bulldozer to Fordwar Position

a sweep along the Hung Loc peninsula, the 2d Battalion, 20th Artillery (Aerial Rocket Artillery), fired SS11 missiles at bunkers on the peninsula. The missiles destroyed the bunkers, thus enabling fifty-five Viet Cong to be captured without a fight.
In mid-October, enemy contacts in the coastal region diminished, and the emphasis of the battle shifted back to the valleys in the west. Capitalizing on the information that elements of the 2d Viet Cong Regiment were regrouping in the Kim Son and Soui Ca valleys, the division quickly airlifted several battalions into the area. On 13 October, the 1st Battalion, 5th Cavalry, located the main Viet Cong province headquarters, including official stamps, radios, documents, and typewriters. On 14 and 15 October, in support of the 1st Battalion, Company A of the 8th Engineer Battalion brought in airmobile engineer construction equipment. A CH-54 "flying crane" lifted a grader and a pneumatic roller into the valley. Teams of engineer soldiers called tunnel rats located, explored, and later destroyed extensive tunnel complexes constructed by the enemy. Sweep operations in the valleys turned up additional caches of equipment and supplies.
During the latter part of Operation IRVING an artillery raid was conducted by A Battery, 2d Battalion, 19th Artillery. Four howitzers 

with crews, 280 rounds of ammunition, and a skeleton fire direction center were airlifted into areas that the enemy had thought were secure to fire on previously selected targets that were beyond the range of other tube artillery. The 280 rounds were fired in less than seventeen minutes, after which the artillery was airlifted back to its base.
By midnight of 24 October the battle was over. The enemy had been unable to cope with the airmobility and versatility of the 1st Cavalry Division (Airmobile). Massive firepower had decimated the enemy's forces, and his long-secure supply bases had been destroyed. While suffering 19 men killed itself, the 1st Cavalry Division had killed 681 enemy soldiers and captured 741. The rapid reaction of U.S. forces allowed the division for the first time to capture more enemy soldiers than it killed. The success of Operation IRVING had a lasting effect on the pacification of Binh Dinh Province.
The major tactical innovation illustrated in Operation IRVING Was airmobile combat. An airmobile operation is one in which combat forces and their equipment move about the battlefield in aircraft to engage in ground combat. In such an operation, helicopters not only transport the forces to the battle area, but also enable them to develop the situation and to reinforce, withdraw, and displace combat power during the battle. The purpose of an airmobile assault is to position fresh combat troops on or near-their tactical objectives. The tactical unit can fly over obstacles and impassable terrain to land at the strategic point in the battle area.
The successful airmobile assaults in Operation IRVING and those conducted by other units in Vietnam were the result of detailed planning by the participating ground units, the aviation support elements, and the combat support and combat service support units. The overall commander of ,an airmobile task force is the commander of the ground unit making the assault. The aviation commander directs the helicopter support units and advises the task force commander on all aviation matters.
Airmobile operations in Vietnam were planned in an inverse sequence, similar to airborne operations. First, the ground tactical plan was prepared. It was the basic airmobile operation plan. In this plan the commander of the assault unit presented his scheme of maneuver and plan for fire support in the objective area. Assault objectives were chosen that insured the accomplishment of the mission. Landing zones were then carefully selected to support the ground tactical plan. A fire support plan was developed concurrently in order to be closely co-ordinated and integrated with the scheme of maneuver.
The next step in the sequence was the development of a landing plan. It insured the arrival of the various elements of combat power at

the times and locations required. The landing plan included the sequence, time, and place for landing troops, equipment, and supplies.
An air movement plan was then prepared, which was based on the previous plans. Its purpose was to schedule the movement of troops, equipment, and supplies by air from pickup to landing. Details such as flight speeds, altitudes, formations, and routes were specified.
Finally, a loading plan was developed. It insured the timely arrival of units at pickup zones and the loading of troops, equipment, and supplies on the correct aircraft at the proper time.
Often, because of rapidly changing tactical situations, the airmobile planning sequence was abbreviated. All elements of the planning were considered, but in a shorter form. The actions of Colonel Root of the 1st Battalion, 12th Cavalry, in Operation IRVING provide an excellent example. Plans were prepared for an airmobile assault by the 1st Battalion on objective 506B. However, when directed at the last minute to assault the village of Hoa Hoi, Colonel Root prepared and assigned new orders while en route by air to the new objective. Sound training and complete standing operating procedures for the ground and aviation units contributed to the quick development of airmobile plans and orders.
Radio communications and prearranged visual signals, colored smoke, and flares were the primary means of communication during airmobile assaults.
Fire support was extremely important during these operations and included artillery, naval gunfire, armed helicopters, tactical aircraft, strategic bombers, and mortars. During a specific operation the task force may have been supported by any or all of these means. All available fire support was controlled by the airmobile task force command group from its command and control helicopter. Preparatory fire on and around the landing zone was usually brief but intense and continuous, with no pause in the firing from the various sources. Fire was shifted from the landing zone only seconds before the first flight of helicopters touched down. The firing was diverted to selected locations to protect the assault force, and then redirected to support the expansion of the objective area. Smoke was often used by artillery or by a specifically equipped helicopter to mask the movement of the assault force.
Division commanders in Vietnam concluded that airmobile assaults greatly increased the speed and flexibility of their operations, extended their area of influence, and provided them with the means to concentrate forces quickly and to move them after accomplishing the mission.
In World War II and in the Korean War, where combat ranges were normally greater than in Vietnam, gunnery errors seldom resulted in friendly casualties. Any round that cleared friendly lines was

usually safe. In Vietnam, however, about 50 percent of all artillery missions were fired very close to friendly positions or into an area virtually surrounded by converging friendly forces. An error could harm U.S. or allied troops or civilians living in the areas of operations. The senior officer in charge of each area of operation was specifically charged with the safety of his troops and of the local population. His fire support co-ordinator worked out the details required to insure this safety. He used such devices as no-fire lines, fire and fire support co-ordination lines, and clearances with the lowest level of the Republic of Vietnam government (usually the district) that had U.S. advisers. Fire support co-ordinators maintained a map marked to show specified-strike zones and no-fire zones, all based on the rules of engagement drawn up jointly by U.S. and Vietnamese high commands. They were applicable to all allied forces and were meant to protect the lives and property of friendly forces and civilians and to avoid the violation of operational and international boundaries. The rules were specific. They covered each general type of operation, such as cordon and search, reconnaissance in force, a waterway denial operation, and defense of a base camp. They also governed the establishment of zones. No-fire zones were those in which persons loyal to the Republic of Vietnam government lived. The rules provided for the different curfew hours which each province chief specified for all Vietnamese civilians in urban centers, along main supply routes, in New Life hamlets, and in the woods and fields. Presumably, all persons who were not in a no-fire zone obeying curfew restrictions were suspect.
Naturally, the rules did not limit the right of a unit to defend itself, and a unit attacked could take necessary aggressive action against the enemy with any means available. As Major General Harris W. Hollis later stated:
The clearest test of the hostility of a target was the receipt of fire from it-prima facie evidence, as it were. In such cases our units or aircraft could return fire as a matter of self-preservation, but only to the degree necessary to deal with the threat. No overkill airstrike could be called down on a Viet Cong sniper without proper prior clearance. I am convinced that this restraint by each responsible commander played a key role in minimizing civilian casualties.
The most serious problem created by clearance requirements was the loss of indirect fire responsiveness and surprise. As a rule, clearances added approximately three minutes' delay for each agency required to take action on the request. Agencies within a unit caused the least delay and complications.
To reduce the time lost in firing missions, nonpopulated areas were frequently cleared in advance of operations and for night intelligence and interdiction fire. Commanders were expected to establish appropriate liaison with local government agencies and with Free

World forces to provide quick request channels and to mark specified-strike zones whenever possible.
With the tremendous increase in the use of aircraft in the Republic of Vietnam came the need to assign responsibilities for their safety from indirect ground fire. Operational responsibility for the air advisory agencies was usually given to the major field artillery headquarters in the area. The agencies were generally located with a battalion operations section. Aircraft entering the area of an air advisory agency usually radioed in for clearance. They were given the locations of all fire or of safe routes to travel. The agency notified aircraft in its area about new artillery missions by calls over its network. The responsibility for all fire above 5,000 feet was passed by the air advisory agencies to the U.S. Air Force.
An important innovation in the Vietnam War was the integration of strategic air power into the ground combat plan. Similar use of heavy bombers in Korea was on a much more limited scale. The Strategic Air Command, with its B-52 bombers flying at extremely high altitudes, out of sight and out of hearing of the unsuspecting enemy, delivered devastating blows against fortified positions. Two B-52 strikes were used in Operation IRVING.
Ground commanders used the B-52's against targets of high tactical value. Enemy troop concentrations in base areas were common targets. When a B-52 target was identified, a request was passed through command channels to a joint Army-Air Force targeting committee. If the request was approved, the target was included in the bombing schedule and the requesting unit was notified. The tactical commander could then complete his plans for using the B-52 strike to its best advantage on the ground. The follow-up operation after the bombing raid, depending on the nature of the target, ranged from a small patrol reconnoitering the area to a large-scale sweep operation involving a battalion-size unit or larger. Artillery was often used following a B-52 strike to hit enemy personnel moving back into the target area.
The tactical mobility furnished by the helicopter and the communications available to the ground commander were effectively used to capitalize on B-52 strikes. While the dust and smoke from the bombs were still in the air, the heliborne assault could begin, taking maximum advantage of the shock and confusion among the enemy troops.
One of the major artillery innovations of the Vietnam War was aerial rocket artillery, commonly called ARA, and later, aerial field artillery. The fire support potential of the helicopter had been appreciated for some time. Gunships, in the form of UH-1 helicopters armed with various combinations of machine guns, rockets, and grenade launchers, had been effectively used throughout the conflict.

Theoretically, however, the gunships provided light fire support rather than the artillery type. Aerial rocket artillery, on the other hand, was organized and employed as artillery. In the words of Lieutenant Colonel Nelson A. Mahone, Jr., commander of the 1st Cavalry Division's 2d Battalion, 20th Artillery (ARA), "We consider ourselves a breed apart, and our success tends to support this." Aerial rocket artillery fire was requested through artillery channels and was usually controlled by an artillery forward observer. ARA was particularly effective in support of airmobile forces beyond the range of the division's ground artillery. Moreover, ARA fulfilled the need for a highly responsive and discriminating means of fire support for the infantry during its most vulnerable phase of an air assault, namely, just after its arrival on the landing zone. Aerial rocket artillery helicopters circling overhead watched over the landing zone and movement of the troops. If necessary, they immediately responded to fire requests by firing directly on the target.
Although ARA was frequently used beyond the range of cannon artillery, it also augmented this fire. ARA was assigned the normal tactical missions of conventional artillery. Normally, however, it was used in general support with control retained by division artillery because of ARA's range and flexibility.
The main armament of the ARA consisted of the M3 2.75-inch folding-fin rocket system mounted on UH-1 helicopters, and later on the Cobra version. In addition, the ARA was capable of using the SS 11 antitank wire guided missiles. SS 11 fire was extremely valuable against point targets, such as bunkers located on hillsides and other enemy fortifications. Medium and heavy artillery in Vietnam was normally located in semipermanent base camps or fire bases to provide support within the tactical area of operations. Continuous fire, or the threat of it, from these weapons caused the enemy to move his base camps and supply caches out of range. The artillery raid was used against these outlying enemy installations by moving to a position in range of the target, firing on the enemy, and then returning to the artillery's base. Medium and heavy self-propelled weapons were particularly well suited for raids, although light and medium artillery lifted by helicopters could be used. In fact, the airmobile divisions achieved excellent results with helicopter-borne 105-mm. howitzers used in this fashion, and they developed expedient methods of clearing jungle artillery bases. This technique was used effectively in Operation IRVING.
In October 1969, the 101st Airborne Division (Airmobile) developed the radar raid in order to extend the influence of its artillery. This type of raid was conducted by frequently moving AN/PPS-4 or AN/PPS-5 radars with security forces to dominant terrain features outside fire bases. These forces could then provide surveillance along 

routes of infiltration previously masked by terrain. By conducting raids within existing artillery ranges, discovered targets could be rapidly engaged.
During Operation IRVING, Company C, 2d Battalion, 8th Cavalry, discovered a tunnel complex in the Nui Mieu Mountains. The complex included five vertical shafts, thirty to fifty feet deep, with horizontal tunnels connecting them. After searching the tunnels, a squad of engineers from the 8th Engineer Battalion destroyed the complex with demolitions.
A significant feature of the war in Vietnam was the widespread use of tunnels and other underground facilities by the enemy. Tunnels were a major factor in the enemy's ability to survive bombing attacks, to appear and disappear at will, and to operate an efficient logistic system under primitive conditions. By the end of 1970, 4,800 tunnels had been discovered. Most of the discoveries were made during sweep operations by Free World military forces. Tunnel complexes were also located through local informers and by means of dogs trained to find underground facilities. An electronic tunnel detector and a seismic detector were tested with limited success. Several techniques have been developed to force the enemy to evacuate tunnels. Tunnel rat teams were formed by many infantry and engineer units to clear and explore tunnels. An exploration kit consisting of headlamps, communications equipment, and a pistol assisted the team. A Tunnel Explorer Locator System was developed to map the tunnel and to monitor the progress of the tunnel rat as he moved through the tunnel. Proven chemical techniques were the use of smoke to locate tunnel openings and a riot control type of tear gas, known as CS, to drive enemy personnel from underground.
After tunnels were cleared and searched, they were destroyed to prevent their further use by the enemy. Methods developed to keep the tunnels from being used again included placing riot control agents in the tunnel, sealing the entrance with explosives, using demolitions to destroy the tunnels, pumping acetyline into the tunnel and igniting the gas by explosives, and using construction equipment to crush the tunnels.
The first use of riot control agents in Vietnam was on 23 December 1964 when CS grenades were air-dropped as part of an attempt to rescue U.S. prisoners being held at a location in An Xuyen Province. In this operation no contact was actually made with the enemy. In February 1965, General Westmoreland informed the senior advisers of the four corps tactical zones that U.S. policy permitted the use of riot control munitions in self-defense. Kits containing protective masks and CS grenades were issued to each subsector advisory team for self-defense. These kits were not intended for offensive use by U.S. troops.

PICTURE: Members of an Engineer Tunnel Rat Team Explore Viet Cong Tunnel.
explore Viet Cong tunnel.

In March 1965, New York Times correspondent Peter Arnett described the use of riot control agents by ARVN forces. His report generated much controversy in both the American and foreign press and led to an examination, by both U.S. military and political agencies, of the pros and cons of the use of CS in Vietnam. An independent action by the commander of the 2d Battalion, 7th Marine Regiment, on 5 September 1965 significantly influenced subsequent policy on the use of CS in Vietnam. The 2d Battalion encountered an enemy force entrenched in a series of tunnels, bunkers, and "spider" holes. Since there was information that women and children were also present, CS was used to help clear the complex. As a result, 400 persons were removed without serious injury to noncombatants. However, on 7 September 1965, all senior U.S. commanders were reminded that "MACV policy clearly prohibits the operational use of riot control agents."
Later the same month, the Military Assistance Command, Vietnam (MACV), decided that the military usefulness of CS warranted a request to higher authority for permission to use it in the upcoming Iron Triangle operation. The request was forwarded to Secretary of Defense Robert S. McNamara, who granted permission for CS to be used in the Iron Triangle operation only. In the following weeks, a much-liberalized policy on the use of CS was developed, and on 3 November 1965 the joint Chiefs of Staff notified General Westmoreland that he was authorized to use CS and CN (another tear gas) at his discretion to support military operations in South Vietnam. This authority was further delegated to the major commanders.
MACV Directive 525-11, dated 24 July 1967, concerned the use of riot control agents in tactical operations. Using these agents in situations where noncombatants were involved was deemed particularly appropriate. The U.S. senior advisers to the four ARVN corps were empowered to authorize the use of CS by U.S. forces in support of the South Vietnamese Army. U.S. advisers at all levels were to encourage their counterparts in the Vietnamese armed forces to use CS and CN whenever such use offered an over-all tactical advantage. The use of riot control agents in situations involving civil demonstrations, riots, and similar disturbances was specifically prohibited without prior approval by the commander of the Military Assistance Command, Vietnam. Riot control agents were treated as normal components of the combat power available to the commander.
The early use of CS was limited by the shortage of standard munitions. The only munitions available at first in operational quantities were the M7 and M25 grenades. Many other ground and air munitions were being developed and later were tested and used in Vietnam.
One of the first uses for M7 CS grenades was to flush caves, tunnels, and other underground fortifications. The 1st Cavalry Division

PICTURE: Riot Hand Granade, CS1, M25A2 
(Airmobile) effectively used CS grenades during Operation MASHER-WHITE WING, which took place in a highly populated area. CS grenades when used on suspected enemy areas enabled 1st Cavalry troops to determine whether the occupants were civilians in hiding or armed Viet Cong. On another occasion, forty-three Viet Cong were pursued into a cave. All forty-three were driven out again, however, when CS hand grenades were thrown into the cave. The only casualty occurred when one Viet Cong refused to surrender.
The burning-type CS grenade, along with HC smoke grenades, was also used in conjunction with the M106 Riot Control Agent Dispenser, dubbed Mity Mite, a portable blower. This system was capable of forcing the Viet Cong and North Vietnamese Army out of unsophisticated tunnel complexes, as well as helping to locate hidden entrances and air vents. The Mity Mite system could not drive personnel from the more complex, multilevel tunnel systems, many of which contained airlocks. However, bulk CS was widely used in tunnel denial operations, in which bags of CS were exploded throughout the tunnels. The 1st Infantry Division's experience indicated that the tear gas remained effective for five to six months if the tunnel was sealed. The efficiency of powdered CS in restricting the enemy's use of fortifications and the difficulty of destroying the numerous bunkers and other fortified structures by conventional explosives led to the development of many techniques for dispensing CS in these enemy defenses.
The 1st Cavalry Division (Airmobile) termed their expedient munition the Bunker Use Restriction Bomb (BURB). The BURB consisted of a cardboard container for a 2.75-inch rocket warhead, two nonelectric blasting caps, approximately twenty-five seconds of time fuze, and a fuze igniter. The device was filled with CS and taped shut. The blasting caps provided sufficient explosive force to rupture the container and to spread the CS49. Other units developed their own expedient CS munitions for contaminating fortifications.
The acceptance of CS as a valuable aid in combat operations led to the development of several weapons systems. These included the E8 riot control launcher; the XM15 and XM165 air-delivered tactical 

CS clusters; the 40-mm. CS cartridge for the M79 grenade launcher; the 4.2-inch mortar CS round; the BLU52 chemical bomb (Air Force); and the XM27 grenade dispenser. The E8 chemical dispenser was used effectively by the 2d Battalion, 5th Marine Regiment, during Operation HUE CITY between 3 and 15 February 1968. The action during this period was characterized by close, intense house-to-house combat. Engagements with the enemy were usually at distances from 20 to 150 meters, with maximum distances of 300 meters. The use of air and artillery forces was limited by weather conditions and by the closeness of the enemy to friendly troops. The tactical situation required almost continual assaults on fortified buildings and some bunkers. The use of the E8 CS dispenser was credited with neutralizing the enemy's firepower during the assaults.
The greatest amount of CS employed in Vietnam was bulk CS1 or CS2 dispensed to restrict the enemy's use of terrain. Contamination of large areas or of terrain not accessible to friendly ground forces was normally carried out by air-delivered 55-gallon drums that contained eighty pounds of CS. The drums were dropped from CH-47 helicopters using locally fabricated racks, which allowed the unloading of thirty drums on the target. The major targets for these drops were known or suspected base camps, rest areas, and infiltration routes.
Air-delivered, burning-type munitions also produced good results as evidenced by the use of thirty E158 air-delivered CS clusters in support of South Vietnamese Rangers on 3 February 1968. The Rangers were heavily engaged by a large Viet Cong force deployed in a factory complex in the Cholon area of Saigon. After several attacks by the Rangers had been repulsed, the CS munitions were dropped into the area by helicopter. The Ranger assault which followed the CS drop was successful.
The use of riot control agents by U.S. and allied forces in Vietnam cannot be likened to the gas warfare of previous wars. Whereas mustard and chlorine gas often resulted in permanent injury and death, CS and CN produced only temporary irritating or disabling physiological effects. Their use saved the lives of many allied soldiers, civilians, and enemy soldiers.
Because of the extensive use of helicopters in the Republic of Vietnam, landing zones had to be rapidly constructed in heavily forested areas, like those surrounding the Kim Son and Soui Ca valleys. The engineers in Vietnam were thus challenged to reduce the landing zone construction time, in order to meet the needs of the quickly shifting tactical situation. Landing zone requirements ranged from the hasty construction of a helicopter pad, from which to provide emergency resupply or medical evacuation, to the development of large landing zones, able to handle sufficient aircraft to support battalion or brigade operations.

Experience gained by engineer units in Vietnam led to the development of landing zone construction kits that contained the necessary tools and demolitions to prepare a landing zone for one aircraft. If the engineer team could be landed near the new construction site, they would rappel from the helicopter or climb down rope ladders. When sufficient area had been cleared, air-portable construction equipment or additional tools and demolitions were lifted in to expand the new landing zone.
The "combat trap" was developed after experimentation. In a joint Army and Air Force effort, an M121 10,000-pound bomb was parachuted from a fixed-wing aircraft or helicopter over the desired landing zone site and detonated at a height that would clear away the dense foliage but not create a crater in the earth. After the combat trap had finished its job, a construction party and equipment were taken by helicopter to the new landing zone to expand it to the desired size.
The key to the success of airmobile operations often was the ability of the engineer battalion to construct landing sites for helicopters and fixed-wing aircraft quickly. To support the airmobile division adequately, air-portable construction equipment was developed for the division's engineer battalion. Engineer equipment that could be moved into the forward areas by helicopter included roadgraders, bulldozers, scoop loaders, scrapers, and cranes, each of which was sectioned and lifted into the objective area in two loads,, and then assembled for operation. Backhoes, small bulldozers, dump trucks, and compaction equipment could be transported in one helicopter lift.
Throughout Operation IRVING the 8th Engineer Battalion used airmobile construction equipment to clear and expand landing zones and artillery positions and to construct defensive positions. On 14 October, a bulldozer, a grader, and a roller were sectioned and airlifted to the command post of the 1st Brigade, 1st Cavalry Division, to expand the existing landing zone and to construct an aircraft refueling area.
The cry of "Medic! Medic!" has been heard in all wars involving the United States, and the company aidman is still the first link in the chain of medical support. In Vietnam the aidman had a new lifesaving tool, the medical evacuation helicopter, better known as Dust-off. Because of the bravery and devotion to duty of these helicopter pilots and crews, many lives were saved. Often Dust-off choppers landed under heavy enemy fire to pick up wounded soldiers or hovered dangerously above the battlefield as an injured man was hoisted up to the helicopter. The seriously wounded were taken directly from the field to a hospital, often bypassing the battalion aid station and the clearing station. This rapid means of evacuation saved many lives and greatly improved the soldiers' morale. Each soldier

PICTURE : Dust-Off Helicopter Hoist Wounded Man from Battlefield

knew that if he were wounded he would be picked up immediately by Dust-off.
Although the helicopter was a great help to the men in Vietnam, it required considerably more engineer support than the Army originally expected. As the commanding general of the engineers in Vietnam, Major General David S. Parker, noted in his debriefing report, "In addition to advanced landing zones, built primarily by division engineers through a number of ingenious techniques, there have been extensive requirements for revetments, parking areas, maintenance hangars, and paved working areas for POL, ammunition, and resupply operations. The construction has increased effectiveness through added protection and improved maintenance."
Parked aircraft were prime targets for the enemy and, as such, were subjected to many damaging small arms, mortar, and .rocket attacks. Therefore, the protection of organic aircraft was a major concern to all commanders. Engineers were charged with providing lightweight, portable, and easily erected revetments for all helicopters without decreasing the helicopter's reaction time. Construction materials included airfield landing mats, plywood, corrugated steel, and soil.
The T17 nylon membrane was an important development for engineer support of airmobile operations. The membrane was designed as a moisture barrier and dust cover for landing zones and strips. It was also used successfully as the surface for unloading aprons and parking areas, thereby greatly reducing construction time. It was not a cure-all, however, since it added no bearing strength to the soil. The blast from helicopters often created large dust clouds, which increased aircraft collisions and maintenance difficulties. The T17 membrane was one way of reducing dust, but peneprime, a commercial composition of low-penetration grade asphalt and a solvent blend of kerosene and naphtha, was the best dust control agent tried in Vietnam. During Operation IRVING, the 8th Engineer Battalion used some 38, 600 gallons of peneprime on helicopter pads, refueling areas, and airfield turnarounds.
Operation IRVING was an excellent example of recent changes in the tactics of war. The airmobile division, with Vietnamese and Korean assistance, demonstrated its flexibility and power as it pursued and destroyed a large enemy force in a populated countryside. The helicopter became an integral part in maneuver plans, division artillery, medical evacuation, and the transport of heavy equipment. The enemy was hit with everything from strategic bombers to tunnel rats, within the confines of special rules of engagement. Psychological operations and population control were also included in the tactical plan.

page created 15 December 2001

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