Hack’s Hardcore Hints #11: Mobile Riverine Force

mpaign Series Vietnam | Hack's Hardcore Hints

In Hack’s Hardcore Hints series, David Galster shares some of his scenario design toolkits for Campaign Series: Vietnam, a work-in-progress tactical platoon-scale wargame.

It’s a pleasure, Campaign Series Wargamers,

If you thought the Marine Corps participated with the Navy in the Mobile Riverine Force, you will be surprised to find that it was the 2nd Brigade, 9th Infantry Division instead. They formed part of the Joint Task Force 117, named the “Mobile Riverine Force.” Why not the Marines? It is because in 1966, the Marine Corps was already heavily committed  in CTZ I (Quang Tri Province,) as Marine Amphibious Force III. This article provides background information on the Mobile Riverine Force that operated in the Mekong Delta.

Origin of Task Force 117

Viet Cong infiltration of the Mekong delta was a severe problem. The US Navy had two other programs, “Operation Game Warden,” and “Operation Market Time,” to patrol the Mekong delta waterways to intercept supplies intended for the Viet Cong.

A need for “strike” capability to find and eliminate Viet Cong led to a joint Army/Navy committee to develop operational plans.  The first administrative unit for a “Mekong Delta Mobile Afloat Force,” (MDMAF) was commissioned at Coronado, California in September 1966. Not long after, TF-117 was designated with the new title, “Mobile Riverine Force.” (MRF)

The MRF would provide “naval” support for infantry brigade plus artillery battalion using the “Brown-Water” Navy’s modified landing craft, support ships, and specially designed assault boats. The strike unit would be a self-contained amphibious assault force, with all support elements except aircraft. (To be added later.)

USA Unit Bades


The 2nd Brigade was commanded by Colonel William B. Fulton, and consisted of the 3rd and 4th battalions, 47th Infantry; the 3rd Battalion, 60th Infantry; and the 3rd Battalion, 39th Artillery. (Towed 105mm howitzers.) 9th Infantry Division was activated for Vietnam duty at Fort Riley, Kansas, in February 1966.

The Navy’s component of TF-117 was a wide variety of ships and boats. The first unit, River Assault Flotilla One (RivFlotONE) was composed of River Assault Squadron 9 (RAS 9) and RAS 11. Each of RAS was sub-divided into two River Assault Divisions: Divisions 91 and 92; Divisions 111 and 112.

RivFlotONE also had a group of support ships including two self-propelled barracks ships, (APB,) a non-self propelled barracks ship, (APL,) two fleet tugs, (YTB,) a landing craft repairship, (ARL,) and a tank landing ship. (LST)

Each RAS had a total of 26 armored troop carriers, (ATC,) five Monitors, two command and control boats, (CCB,) one Refueler ATC, 16 assault support patrol boats, (ASPB,) an artillery barge, and an explosive ordnance detachment. (EOD)

In 1967, Task Group 117.3 was composed of USS BENEWAH (APB-35), USS COLLETON (APB-36), APL-26 with USS KALISPELL (YTB-784) and USS WINNEMUCCA (YTB-785) attached, USS ASKARI (ARL-30), and a supporting LST, plus other support and salvage craft. The MRF base was at Dong Tam on the My Tho River  branch of the Mekong River Delta.

Map of the Mekong River Delta in South Vietnam

Details of Ships and Boats

Armored troop carriers, ATC were the main craft of the RAS. They were modified LCM-6 landing crafts, and were 15 m long and 4.6 m wide. Two diesel engines powered twin propellers.

An ATC could carry a full infantry platoon. Armed with three 20mm cannon or Mk 19 automatic grenade launcher and two 20mm cannon, up to two .50 caliber machine guns and four 7.62mm machine guns, two Mark 18 40mm grenade launchers, plus various small arms, the ATCs not only landed troops, but also re-supplied them and provided fire support during operations.

Armored Troop Carrier (ATC)

The refueling ATC boat was similar, except the well deck space for troops carried pumps and rubber fuel bladders instead. Either diesel fuel for boats or JP-4 for helicopters could be carried.

The “Monitor” provided fire support. These had the same superstructure as the ATC but forward, they had an open well deck, with a Mk 2 Mod 0 Navy 81 mm mortar and two 7.62mm machine guns. A rounded bow replaced the door and ramp. The redesigned bow mounted a 40mm cannon (with a co-axial 50 caliber machine gun) enclosed in a turret. The 40mm was the main gun. In addition, at least two Mark 18 grenade launchers were carried along. Later, Program 5 Monitors replaced the 40mm turret with the 105mm turret of the Marine Corps LVT(H)-6 amphibious tractor (Amtrac).

One modification was called the “Zippo” boat. Instead of the mortar, there were two M10-8 flamethrower turrets, and associated fuel and compressed air equipment. The flamethrowers would burn away the dense foliage along the riverbanks to reveal enemy bunkers. The Zippo was hated and feared by the VC.

The command and control boats, CCB were similar to the monitors, except that the mortar pit was replaced with a radio shack.

In case you are worried, the Campaign Series Vietnam game includes the ATC, Program 4 Monitor, Program 5 Monitor (Howitzer,) Program 5 Flamethrower (Zippo,) and the CCB.

A scenario series called “A week in … The Mekong Delta – May 1967” is planned for Campaign Series Vietnam. It will feature lengthy scenarios dealing with My Tho, Ap Bac 2 Battle, and  operations in the Cam Son Base Area.

An ATC unit for CS Vietnam

Campaign Series Graphic of an ATC

Monitor M-92-1

Monitor M-92-1

The Assault Support Patrol Boat, ASPB was similar in size to the ATC but with a more streamlined hull. The two 12V71 diesel engines drove twin propellers. The superstructure utilized spaced armor and bar armor was fitted later. Crew was 5 men. Early boats had a Navy 81mm mortar or two 7.62mm Mk 21 machine guns or .50 machine guns. The turrets were designed for 20mm guns, .50 machine guns, 7.62mm machine guns, and a 40mm automatic grenade launcher. The ASPB underwent several improvements in armor and armament during the years 1967 to 1971.

The ASPB was employed for ambushes, patrols, special operations, reconnaissance, and escort missions. It was also designed to serve as a minesweeper, and was fitted with a mine countermeasure chain drag. Lighter and faster than the Monitor, the ASPB was not as heavily armed or armored.

Assault Support Patrol Boat

The 328-foot USS Benewah (ABP-35,) self propelled barracks, was built on a World War II LST-542 class hull. Like the riverine craft, fire superstructures of these ships carried the same bar armor to protect them from rockets and recoilless rifle fire. APBs USS Benewah and USS Colleton carried two quad 40-mm guns, two 3”/50 dual-purpose guns,  eight .50 machine guns, and eight 7.62mm machine guns.

Each APB could accommodate about eight hundred troops, and provide support for the riverboat crews. Each APB had an extensive communications system. The USS Benewah (APB-35) was equipped to serve as the brigade and flotilla flagship.

Self-Propelled Barracks Ship

Combat Operations

Typical combat operations involved first sweeping the assault area with the ASPBs for reconnaissance. Monitors follow, and fire on enemy troops to suppress them while the ATCs would move in, and offload infantry assault troops.

Artillery barges would bring the 105mm howitzers to within an effective range, (11000m) and provide support. Reinforcements might be available from a self-propelled barracks ship.

Troops could also be brought in by helicopter to LZs for blocking purposes. A graphic depicting a hypothetical operation is shown below.

Some real operations included  Truong Cong Dinh, in which  Mobile Riverine Forces conducted a series of combined riverine and airmobile operations, beginning east of My Tho. Operations were supported by the 3rd Battalion, 34th Artillery of the US, which established a fire support base on the north bank of the My Tho River, 16km east of the city.

The 4-47 INF Battalion came under heavy small arms and automatic weapons fire just west of My Tho. This continued until 22:25, but the following day, the troops met no VC in the area. In response to new intelligence, moved again into the area of operations, where there were several firefights occurred the rest of the day. The most significant occurred at 17:15 when Company B, 4-47  INF made an assault landing by helicopter, and was fired upon by a VC force from well entrenched positions along the southern edge of the LZ. Five helicopters were brought down. Throughout the evening and into the night, as other elements maneuvered in support of Company B, there was sporadically heavy fighting in the area. At 03:00, the fire support base was attacked by mortars, sinking two artillery barges along with four 105-mm howitzers. The 4-47 INF continued their sweep of the battlefield without finding any VC, and returned by ATCs to the Mobile Riverine Base at Dong Tam in the late afternoon.

Riverine Operations Map


The Mobile Riverine Force was well equipped, with innovative technology. It was a very capable force, and was effective. There were still many challenges for finding Viet Cong, and avoiding ambushes, but several countermeasures were employed like using flamethrowers, to deal with these issues.


“The Brown Water Navy in Vietnam – Part 3,” by Robert H. Stoner, GMCM (SW)(Ret)

“Mobile Riverine Force,” Wikipedia

“Operation Truong Cong Dinh,” Wikipedia

“Riverine Warfare- Vietnam I,” https://weaponsandwarfare.com/2015/08/26/riverine-warfare-vietnam-i/

Hack was part of the 9th Infantry Division, but not the Riverine Force. He commanded the 4-39th Inf Battalion.

mpaign Series Vietnam | Hack's Hardcore Hints


CS: Middle East 50% Off at Matrix Holiday Sale 2018

Campaign Series: Middle East is on sale

That time of the year again, folks… Matrix Holiday Sale is here!

CS: Middle East 50% Off

CS: Middle East 50% Off

And with it, Campaign Series: Middle East 1948-1985 is 50% Off!

Still on fence? Now is as good time as any to give this tactical platoon scale wargame a go:

Campaign Series Middle East Out Now

CS: Middle East has been updated to version 2.0

The offer is valid from 21 November, 2018 to 13 January, 2019. Get your’s while supplies last!

Hack’s Hardcore Hints #10: Artillery and Firebases

mpaign Series Vietnam | Hack's Hardcore HintsIn Hack’s Hardcore Hints series, David Galster shares some of his scenario design toolkits for Campaign Series: Vietnam, a work-in-progress tactical platoon-scale wargame.

It’s a pleasure, Campaign Series Wargamers,

Did you ever imagine that there were upwards of 8000 firebases established in Vietnam between 1945 and 1975? Naturally, “only” a couple thousand were active at any one time. Let that sink in.

This article covers US artillery in Vietnam in more detail, and describes the important role that fire support bases played in the war.


Over half the artillery units were under division artillery or DIVARTY. Infantry divisions typically had three 105mm howitzer battalions, and one 155mm/8in. howitzer battalion.

Artillery battalions all had a headquarters plus a headquarters and service battery (HHSB). This included operations, fire direction, administrative, service, liaison, medical sections, communications, plus supply and maintenance platoons.

Field artillery battalions had three batteries, (A, B, & C) with the exception of 155mm/8in. howitzer battalions. These had three 155mm towed howitzer batteries, and one battery of 8in. SP howitzers. Towed and SP 105mm and 155mm howitzer batteries had six tubes. Eight-inch SP howitzer and 175mm SP gun batteries had four tubes.

Sometimes 105mm battalions formed a provisional Battery D (Delta) to adapt to operational needs. Typically, two howitzers were drawn from each of two regular batteries. Crews were smaller, and headquarters personnel were drawn from the headquarters battery and/or other howitzer batteries. One unique organization was Battery D, 2nd Battalion, 13th Artillery of II FFV Artillery. Known as the “Jungle Battery,” it had three 105mm, and three 155mm howitzers. It supported Special Forces in III and IV CTZ.

A total of 63 towed and SP 105mm, 155mm, 175mm, and 8in. battalions served in Vietnam. There were also four separate 105mm batteries, five target acquisition batteries, two aerial rocket battalions and two batteries (rocket-firing helicopters), and two aviation batteries (observation helicopters). These units were assigned to field force/corps and division artillery, separate brigades, and artillery groups.

The “Guns”

The main calibers were 105mm, 155mm, 8 in. and 175mm. The 105mm was the most common, and the initial model was M101A1. This howitzer was virtually the same 105mm that had been used by US forces since World War II.

In 1966, a new 105mm towed howitzer, the M102, was received in Vietnam. Replacement of the old howitzers continued steadily over the next four years. Many seasoned artillerymen did not want the old cannon replaced. They had become familiar with its every detail, and were confident using it.  The waist-high breech made it easier to load, and it had higher ground clearance when towed.

However, the M102 was substantially lighter, weighing little more than 1.5 tons, whereas the M101A1 weighed approximately 2.5 tons. So, more ammunition could be carried during heliborne operations, and a 3/4-ton truck rather than a 2½-ton truck was its prime mover for ground operations. Another M102 advantage was that it could be traversed a full 6400 mils. (360°)

The towed M114 155mm howitzer was the medium duty weapon. The 155mm self-propelled (SP) version was the M109.

The 8 in. (heavy) howitzer was self propelled, and known as the M110. The M107 175mm self- propelled howitzer was another large gun in the “heavy” category.

US Artillery Systems used in Vietnam




M102 105mm Howitzer

M114 155mm Howitzer

M114 155mm Howitzer



Fire Support Bases

So, just what does the term “firebase” or “fire support base” mean? Any position with heavy weapons could fall in this classification, but it had a more definite meaning in Vietnam. To better understand this, there were several types of bases.

The largest was the “base camp.” These were permanently fortified, and were the headquarters for large organizations like divisions or corps. They typically had an airfield, capable of landing large fixed wing aircraft.

A “forward operating base” (FOB) was smaller than a main base, but was also permanently fortified and had an airfield. A division or a brigade task force sized unit could have a headquarters here.

The “fire support base” FSB was smaller than an FOB. The fortifications were fairly permanent, but the LZ was for helicopters (Chinook) rather than fixed-wing aircraft. These typically housed a single artillery battery, and were often the headquarters for an infantry battalion operating in the area.

A “landing zone” or (LZ) could be anywhere needed to land helicopters. Most were temporary and not fortified.

French forts had existed since colonial times. These were small, but permanently fortified. However, French forts were generally not adequate for combat conditions in the 1960s war years.

A “strategic hamlet” was lightly fortified and controlled by local militia. In Vietnam, a “hamlet” was a discrete portion of a “village” which might cover several kilometers.

Finally, there were “night defensive positions,” (NDP)  occupied by infantry for just one night. Of course, it might include foxholes and possibly some claymore mines, but was otherwise not heavily fortified.

Firebase Combat Role

The concept of a firebase or FSB was to house an artillery battery that could support infantry operations within its range. For the 105mm howitzers, this range was 11000 meters. So, an FSB could support an area 22000 meters, or 22 km in diameter. Infantry units assigned to this region could patrol and conduct operations while relying on artillery support.

Naturally, higher caliber guns extended the radius of operations. And, by locating multiple firebases spaced apart from each other, an entire district could be covered by artillery fire, provided the spacing was within two howitzer ranges. (22 km minimum)

Even if they were spaced 22 km apart, the number to cover all of South Vietnam, 1000 km long, would not have been manageable. Therefore, MACV forces had to concentrate their operations and FSBs on certain select areas at any given time.

Layout and Defenses

Naturally, the NVA developed sapper units to attack and destroy firebases. So a firebase had to have adequate defenses. The location was usually set in a clear area, with at least 100 meters clear all around the firebase. This gave garrison defenders good line of sight to attackers. Often, the jungle had to be cleared by explosives or bulldozers. The perimeter usually had trenches with bunker strongpoints, and elevated observation towers at intervals. Wire barriers, (barbed or concertina wire,) surrounded the trenches. The total firebase size was at least 200 to 300 meters in diameter.

Within the firebase perimeter, there was an LZ, command and communication bunker, fire direction control (FDC) bunker, and the gunpits. Usually an artillery battery of six guns were assigned, so firebases typically had six gunpits. Living quarters for artillery crews and infantry were also included in the complex. Where infantry “D” companies existed, they might be used for the defensive garrison.

Each battery position, including gunpits and the FDC were arranged in circular fashion to allow for the “6400 mil concept” or ability to fire quickly in any direction. Often, there would be additional berms, sandbags, and even wire obstacles around gunpits to fortify them as “inner” defenses. Each gunpit had ammunition racks, an HE shell bunker, crew quarters, a powder pit and bunker, and a fire barrel.

FSB Hill 4-11

A typical Vietnam era firebase was FSB Hill 4-11, which was active near  Quang Ngai City, during 1969 – 1970. It was the headquarters for the 3rd Battalion, 1st Infantry. The artillery unit was Delta battery, (M102A1 105mm Howitzers) 6th Battalion, 11th Artillery.

See numbered items in Yellow:

1   Command and Communication Center

2   Landing Zone, LZ

3   Gunpit

4   FDC Bunker

5   Defensive strongpoint

6   Clear fire zone


The artillery fire support bases played a significant role in US combat operations in Vietnam. It is important for Campaign Series wargamers to understand how they fit into the US strategy for conducting the war. They had the advantage of providing artillery support over a large operating area. They were vulnerable to NVA sapper attacks in particular, and so had to have adequate fortifications, and garrison troops to support them.


“Vietnam Firebases 1965-73,” Randy E M Foster, Illustrated by Peter Dennis

I get the impression that Hack really liked having artillery support. He discusses its need in his Vietnam Primer. Apparently, it was effective against VC tunnels.

mpaign Series Vietnam | Hack's Hardcore Hints

Hack’s Hardcore Hints #9: US Armor and Mechanized Forces

mpaign Series Vietnam | Hack's Hardcore Hints

In Hack’s Hardcore Hints series, David Galster shares some of his scenario design toolkits for Campaign Series: Vietnam, a work-in-progress tactical platoon-scale wargame.

It’s a pleasure, Campaign Series Wargamers,

Did you know that Patton commanded an armored cavalry regiment in the Vietnam War? Well, not exactly General Patton of WWII fame, but his son, George S. Patton IV, was the commander of the 11th Armored Cavalry Regiment in 1968. This article covers armored and mechanized forces in Vietnam.

Armor Introduction to Vietnam

Armor was originally thought to be of little use in Vietnam, but General Westmoreland realized its value for route security and sweeps. The 11th Armored Cavalry Regiment (11th ACR) was deployed to Long Binh in the fall of 1966. The “Blackhorse Regiment” continued to serve in CTZ III north of Saigon.

11th ACR participated in many notable operations, including Cedar Falls, Junction City, Manhattan,

Kittyhawk, Tet Offensive, Adairsville, Alcorn Cove and others. These were search and destroy missions, but would later be known as reconnaissance in force (RIF) operations.

11th Armored Cavalry Regiment Patch

11th Armored Cavalry Regiment Patch

US Armored Fighting Vehicles in Vietnam

As Huey helicopters were the main transportation means for airmobile units, the main vehicle used for transporting mechanized troops was the M113A1 armored personnel carrier. (APC) It was a fully tracked vehicle developed by Food Machinery Corp (FMC). First tested in April 1962, the M113 was the most widely used armored vehicle of the US Army in the Vietnam War. The nickname “Green Dragon” was given by the Viet Cong, as it was used to break through heavy jungle thickets to attack and overrun enemy positions.

Aluminum armor made the M113A1 much lighter than earlier vehicles; it was thick enough to protect against small arms fire, but light enough for air transport, and moderately amphibious. It was powered by a 6-cylinder Detroit Diesel 6V53T engine. It could carry eleven infantrymen, and had a M2 Browning .50 Caliber Machine Gun.

Troop egress was through a rear drop ramp, in which a door was set. Mines were a real threat. The floor was provided with two layers of sandbags, and further covered with ration and ammunition boxes.

An important improvement was  developed which was known as the “ACAV.” (Acronym coined by 11th ACR cavalrymen.) The ACAV kit included shields and a circular turret for the .50-caliber M2 machine gun, and two M60 machine guns, with shields for the left and right rear positions, and “belly armor”  – steel armor bolted onto the bottom. This transformed the M113 into an assault vehicle, and was used for scouting.

The main battle tank was the “Patton” tank, 52-ton M48A3. It mounted a 90mm M41 gun with 62 rounds plus a coaxial 7.62mm M73 machine gun. 90mm ammunition included HEP, armor-piercing-tracer, armor piercing capped-tracer, HEAT, white phosphorus, canister, and anti-personnel tracer (“flechette”). A .50 cal M2 machine gun was mounted in the enclosed commander’s cupola, but often either the .50 cal, 7.62mm M60, or .30cal M1919A4 were mounted atop the cupola for a better field of fire. The crew consisted of the tank commander (TC), gunner, loader, and driver. Its 750 hp diesel engine gave it a speed of up to 30mph and a cruising range of 310 miles. The M48A3 was used in “D” companies of armored cavalry squadrons.

US Armored Fighting Vehicles Vietnam

In 1968, Colonel George S. Patton IV (son of World War II General Patton), commander of the 11th ACR in South Vietnam recommended to General Creighton Abrams that one squadron from a division and the other from theater command be issued the army’s new aluminum tanks (M551 Sheridans) for combat testing. Abrams concurred, and in January 1969, M551 Sheridans were issued to the 3rd Squadron 4th Armored Cavalry, and the 1st Squadron 11th Armored Cavalry.

Another important variation of the M113 was the M106A1 mortar carrier. The crew compartment was fitted with a mount for a 4.2in. mortar, with a large round opening above for firing.

The last major armored fighting vehicle was the  155mm M109 self propelled (SP) howitzers. A battery of these were included in armored cavalry squadrons.

Armored Cavalry Unit Organization

The basic component was the armored cavalry platoon. Consisting of 38 men and nine vehicles, it included the following arrangement:

11th Armored Cavalry Regiment Organization

*The 11th Armored Cavalry Regiment replaced the two Patton tanks with M113A1 ACAVs.

The armored cavalry troop was a company-level organization with three armored cavalry platoons, and a  HQ platoon consisting of two M113A1 ACAVs and 14 men, and a support section with two M113A1 APCs, plus an 18-man maintenance section with one  M113A1

APC and a M578 recovery vehicle.  These troop organizations were based on TO&E 17-I07E, 1966.

The armored cavalry squadron consisted of a headquarters troop, (HHT,) three armored cavalry troops, “D” tank company, (17x M48A3 tanks,) plus a SP howitzer battery. (TO&E 17-105E).

Finally, the armored cavalry regiment was the largest armored organization in Vietnam. The 11th Armored Cavalry Regiment was organized per following table:

Armored Cavalry Unit Organization

The Air Cavalry Troop was used for reconnaissance and artillery spotting. These had eight OH-58D Kiowa Warrior helicopters and crews.


A limited amount of armor was used in the Vietnam War, in the CTZ III where the terrain was favorable. Some interesting innovations were made with armored warfare in Vietnam, even though the overall theatre was not suited for it.

I believe that there is value in knowing about the history of the 11th Armored Cavalry Regiment. But our dear “Hack” probably wasn’t impressed by the armor forces. His forte was in guerilla warfare and counterinsurgency.

mpaign Series Vietnam | Hack's Hardcore Hints

Hack’s Hardcore Hints #8: Airmobile Infantry

mpaign Series Vietnam | Hack's Hardcore Hints

In Hack’s Hardcore Hints series, David Galster shares some of his scenario design toolkits for Campaign Series: Vietnam, a work-in-progress tactical platoon-scale wargame.

It’s a pleasure, Campaign Series Wargamers,

As I am sure you know, helicopter airmobile forces were developed during the Vietnam War. This article provides an overview of this development, and its organization and execution during the war.

Cradle of the “Chopper”

It all began with Igor Sikorsky, who designed and built the VS-300 helicopter in 1939. It was too primitive for combat in WWII, and improved versions saw only limited use in the Korean War. But in 1954, Major General James Gavin, 82nd Airborne Division commander in WWII, wrote a Harper’s Magazine article, “Cavalry, and I Don’t Mean Horses.”  This inspired Army leadership to develop a tactical doctrine for helicopters in combat.

The Rogers board was formed in 1960 to match aircraft industry proposals with Army needs. The Bell XH-40 design was one of the utility helicopter proposals considered that eventually became the UH-1. In 1962, Robert McNamara pushed for major advances in tactical mobility and aerial combat capabilities. The Howze Board started a testing and evaluation program for all aspects of airmobile unit organization and operations.

Airmobile Division

The Army had a  challenging vision for the “airmobile division.” Rapid movement to key areas over any terrain could deliver fresh troops for immediate combat. Rapid, high intensity operations could be maintained, and it could respond quickly to tactical situation changes. The force could disengage, and move swiftly to fight at another point, a considerable distance away. As the enemy presented opportunities, these could be promptly exploited. Movement over rivers, swamps, mountains, jungles, or areas of destruction and contamination was feasible. Extensive aerial fire support was available, and the division could support itself logistically with organic aircraft.

The organization of an airmobile division was similar to an infantry division, except that it had an aviation group, over 400 helicopters, and had fewer trucks and other vehicles. Heavy equipment items, particularly engineering ones, were replaced with lighter equipment. The composition of an airmobile division is shown in the following table. The first airmobile division was the 1st Cavalry Division (Airmobile) which was built from assets of the 11th Air Assault, 2nd Infantry Division, and the 10th Air Transportation Brigade. It was deployed to Vietnam in August, 1965.


Airmobile Division OOB

1st Cavalry Division Patch

1st Cavalry Division Patch

Airmobile Infantry

The battalion structure of airmobile infantry was very similar the regular versions, except for heavy weapons. The regular 4.2 in. mortar platoon was replaced by 81mm mortars. The airmobile rifle company had 164 soldiers vs 174 for regular infantry. The 106mm recoilless rifles were omitted for airmobile companies. Airmobile rifle companies had a headquarters, three rifle platoons, and a weapons platoon. Naturally, these were trained for helicopter operations.

Air Cav Rifle Company OOB

Rifle platoons were armed and organized with 44 men. The platoon headquarters had a platoon leader, platoon sergeant, and an RTO. The three ten-man rifle squads consisted of a squad leader and two fire teams (Alpha and Bravo) with a team leader, an automatic rifleman, and a grenadier. One team had two riflemen and the other had one. The 11-man weapons squad had a leader, two machine gunners and assistants, two antitank gunners and assistants, and two ammunition bearers.

Battalions had variations, however. When the 1st CavDiv deployed to Vietnam, most of its battalions reorganized their 106mm RCLR (recoilless rifle) antitank platoons as machine-gun platoons with M60s and reassigned the weapons carriers to other duties. This allowed the crews to reinforce firepower with a usable weapon. One battalion, however, the 2-7th Cavalry, simply armed the crews with M16 rifles, and each man carried two or three light antitank weapons (LAWs), which added little to unit firepower. These platoons disappeared as manpower dwindled.

Company weapons and mortar platoons gradually disappeared. Some companies retained one or two mortars for use in firebases. The antitank section was sometimes retained strictly as mortar ammunitions bearers, carrying three 9 lb rounds each. Other companies maintained a 12-15 man mortar “platoon” with only one 81mm, which may not always been taken to the field. If the mortars were not carried, the platoon served as riflemen. In dense jungle, there was no overhead clearance to fire mortars. In some instances, one or more mortars might be air lifted to defend a night location or temporary firebase. Often they were used only for illumination.

Certain considerations led to having a fourth rifle company. US Army, Pacific published General Order 149 on September 10, 1967 for authorization. The three-company battalion was effective in conventional linear operations, but in Vietnam more flexibility was needed. Four companies allowed one to be used for firebase defense, or as a reserve, or reaction force. These were implemented through “Company D Packets.” These were raised from recruits, officers, and NCOs drawn from stateside units plus recent OCS and Noncommissioned Officer School graduates. They were given minimal training, and deployed starting in August 1967.


The most familiar name “Huey” came from the original designation HU-1A. This was a medevac helicopter, but could carry six troops. But, there were other types of helicopters and the designations were set by the Air Force in 1948.

AH    Attack

CH    Cargo

OH    Observation

UH    Utility

Series modifications were indicated by letters “A” upwards.

Army helicopter types were named after Indian tribes, Navy and Marine names usually had the “Sea-” prefix. Many slang terms evolved. Helicopters were “choppers, helos, birds, or helos. UH-1 helicopters carrying troops were called “slicks.” Attack helicopters were called “gunships,” but Cobra attack helicopters, AH-1G were called “snakes,” and UH-1B or UH-1C were known as “hogs”.

The Bell UH-1 series was very common in the airmobile units. The UH-1B was later fitted with two forward 7.62mm machine guns, two door guns, rocket pods, and a grenade launcher. These were mostly used as gunships. The aerial rocket artillery, (ARA) application was the UH-1C with two 24-tube rocket pods. The UH-1D became the most common troop carrier with 11-man capacity.

The twin rotor Boeing Vertol CH-47A Chinook was a medium cargo helicopter. It could sling a 105mm howitzer or carry 33 troops. The heavy lift helicopter, Sikorsky Tarhe CH-54A, was very important for moving heavy artillery like the 155mm howitzers or construction equipment, like bulldozers.

Light observation helicopters (LOH) were known as “Loaches,” but this name is mainly associated with the OH-6 Cayuse. The Bell H-13 or OH-13 “Sioux” was widely used for reconnaissance and for artillery observation.

AH-1G Attack Helicopter

AH-1G (Bell 209) Huey Cobra “Snake”

Army Aviation Units

Each airmobile division had an aviation group, which consisted of two assault helicopter battalions, an assault support helicopter battalion, (also called “Medium,”) and an aviation support company. The assault helicopter battalions had a headquarters company, an aerial weapons company, and and three assault helicopter companies. These were the ones that had on-to-one correspondence with the airmobile infantry company, and carried them to landing zones. (LZs)

An aviation company, regardless of type had two to four platoons, and also a flight operations section.

This section’s function was to establish and operate the company heliport and assist headquarters with operational control. The company also had a service platoon with maintenance and service sections.

CS Vietnam Sample OOB for an Aviation Support Group

CS Vietnam Sample OOB for an Aviation Support Group

Army Aviation Company TypesAir Assault Operations

Airmobile assaults were very complex operations, and required much coordination. The basic operation was rifle company insertion. The planning begins the day before, when the mission was requested, and various units tasked.

The landing zone is selected based on the mission and objective of the rifle company. Selection was critical. Alternate LZs were designated if enemy action, or terrain made the primary on unusable. Proximity of LZs to enemy positions was also critical.

A temporary fire support base is set up on a hill top, and fires coordinated with other FSBs.

OH-6 helicopters recon the LZ and surrounding area.

Troops load on the UH-1Ds at their assembly area. These are organized in “sticks.” The size and number of these depended on number of available aircraft, and lift restrictions imposed by air density and altitude. Excess squad members who could not be loaded on the same chopper are collected in additional sticks and landed later. Troops approach the helicopter from the nose for the pilot’s view. Avoiding the tail rotor was also critical. Entry could be on either side of the UH-1D.

Artillery preparation begins before the “lift” birds arrive. This usually lasts about ten minutes, and plotted along treelines or suspected enemy positions. The last rounds were timed to end two minutes before the lift arrives, and were signaled with white phophorus smoke.

A UH-1 command-and-control helicopter arrives on location, and serves as air traffic control.

Just prior to the lift, AH-1 gunships fire on the LZ perimeter with machine guns, rockets, and grenade launchers. They had to pull out of their run as the troop-carrying “slicks” appeared. And then, the gunships would orbit on call. Because of their ammunition load, they carried limited fuel, and could stay on station only a short time.

The flight formation might be an arrowhead or diamond, or staggered trail. The flight would land in the same formation as used in the flight. Inserting a 100-man rifle company required about 15 helicopters. But sometimes LZs were limited to land only four at a time. So the serial had to be subdivided into flights that were sized to the LZ limit. Flights could arrive in intervals as short as 30 seconds.

A low flying UH-1 lays a smoke screen along the treeline, or between enemy positions, and the LZ.

The first troop lift of UH-1 “Slicks” arrive. The passengers were alerted prior to arrival. The whole process became routine for infantrymen after a couple missions. Troops disembarked only on orders of the crew chief. If the chopper were hovering, they would swing their legs over the side and step off the skid. If unloading under fire, soldiers knew not to fire from the chopper, even if the door gunners opened fire. Of course, if there was enemy fire, the flight commander might cancel the landing.

Two further lifts were needed to deploy the whole company.

CSVN Representation of an Air Assault

CSVN Representation of an Air Assault


Airmobile infantry was an amazing innovation in military technology. The effort to implement it was tremendous in terms of helicopter development and manufacturing, training, and devising an operational doctrine. But, it gave the Americans an added advantage in mobility and firepower. Although paratroop units did not completely vanish, large parachute operations became passé.


“Vietnam Airmobile Warfare Tactics,” Gordon Rottman

mpaign Series Vietnam | Hack's Hardcore Hints