How Multiple Machine Gun Mounts Shaped Wars in Latin America

By Julio A. Montes

As they overflew the Swan Islands, the 15 C-130s descended to tactical altitude, and the 2nd and 3rd Rangers prepared to jump. Minutes later, the planes came close to the target, a small airfield one mile inland on the south side of the Panamanian isthmus; they were coming in at 500 feet from the ground, a dangerous low altitude to drop the paratroopers. Then the sky lit up with fire from a 14.5mm machine gun. Ground fire was directed against “Chalk 7”—call sign for the leading C-130—and “Chalk 3” behind it. On the ground, waiting for the Rangers at Rio Hato were elements of the 6th “expeditionary” mechanized and the 7th “Macho de Monte” rifle companies of the Panamanian Defense Force (PDF). This translated into 520 strong, who were equipped with assault rifles, 42 machine guns, nine old bazookas, four 90mm M67 Recoilless Rifles (RRs), 23 mortars, six ZPU anti-aircraft (AA) machine guns and 19 armored vehicles. At H-hour, two F-117A Stealth fighters had dropped two 2000-pound bombs to stun and confuse the PDF troops in a futile attempt to convince them to surrender. Instead, the explosions had alerted the garrison and missed the single 14.5mm ZPU deployed to defend the airstrip. Panama had acquired 20 ZPU-4s, and these were distributed among strategic sites to use as air defense as well as ground defense weapons. These were the first hours of Operation Just Cause, the U.S. invasion of Panama on December 20, 1989.

The Rangers finally silenced the ZPU at Rio Hato with the help of an escorting AC-130, while elements of C Company, 3rd Ranger Battalion engaged forces at Torrijos Airport, destroying another ZPU-4 and three M2 anti-aircraft machine guns. The operation was a well-executed attack that involved some 26,000 U.S. soldiers who overwhelmed the PDF and captured dictator Manuel Noriega. The troops attacked two dozen targets throughout the country, finding stiff resistance in some areas, particularly from troops manning those heavy machine guns and 120mm mortars.

Soviet Quads

The ZPU-2 (twin mount) and ZPU-4 (quad mount) were widely used by Central American rebels and military forces alike, including the Costa Ricans and Panamanians. Both the Russian and Chinese variants are found in Central America. The Type 56 is a Chinese copy of the Soviet ZPU-4 quadruple anti-aircraft machine gun (AAMG) that was first introduced in 1949 and then type-classified in 1956. The ZPU-4 multiple machine gun mounts (MMGMs) had actually been used for the first time in Central America on June 29, 1979, when a rebel gun fired against a Nicaraguan National Guard T-33A while strafing Sandinista National Liberation Front (FSLN) positions at Peñas Blancas. The FSLN managed to shoot down planes in Chinandega, another in Nueva Segovia, one more in Chontales, one in Rivas and one in Condega, Estelí.

By far, Nicaragua would become the largest user of the ZPU. Between 1982 and 1985 Sandinista Air Force and Air Defense (FAS-DAA) created Anti-Aircraft Artillery Groups (GAAAs), with the First GAAA becoming part of the “Oscar Turcios” Tank Brigade in 1982, and integrating it with, among others, three ZPU-4 batteries. At the time, there were 60 ZPU-4s (14.5mm) and 42 ZU-23-2s (23mm) in Nicaragua. In 1983, the EPS (Sandinista Popular Army) established the Artillery Brigade “Omar Torrijos Herrera,” adding a GAAA. There were seven GAAAs corresponding to the seven military regions; one more GAAA was assigned to the Sandinista Navy (MGS) and another one to the High Command Reserve (RAM). Three AAA Regiments, with two or three GAAAs each, were established in 1985 to defend Managua (RAAA 1014, 1316 and 1820).

Another popular MMGM in the region was the Czechoslovak TK vz. 53. A quadruple mount was developed and denominated “quad 12.7mm Vz. installation.53” ( or M1953 AA quadruple MG) in 1953, and production started at the Vsetin plant in 1955. The mount consists of the gun operator sitting behind the four machine guns. Each gun was fed from a 30-round cylindrical box. It had a detachable wheel system and weighed 558kg in firing position. The system had an effective range against aerial targets of about 1,500m. The Czechoslovak LSD Vz.53 was smaller and much lighter than the ZPU-4, so it has been often mounted on flat beds of Unimogs and other high mobility light trucks. It was supplied in large numbers to Cuba where it proved effective against low-altitude air targets, shooting down or damaging several Douglas A-26Bs that were supporting Assault Brigade 2506 during the invasion of Playa Girón at the Bay of Pigs in April 1961. The M53s also engaged U.S. reconnaissance planes during the 1962 Cuban Missile Crisis and were deployed to Angola and other parts of Africa. A number of Cuban M53s were also supplied to Granada. This Caribbean nation received some 60 crew-served anti-aircraft weapons to include 24 ZSU-23 guns.

Operation Urgent Fury, the U.S. invasion of Granada, took place on October 25, 1983. The 1st Ranger Battalion assaulted Point Salinas airfield, finding stiff anti-aircraft fire from M53s and ZSU-23s. Special Forces came later using three Blackhawks of TF-160 to attack Richmond Hill Prison. As the UH-60s engaged, they came under fire from air defense artillery (ADA) emplaced at Fort Frederick, a fortress of the People’s Revolutionary Army overlooking the prison 150m above it and 500m to the east. The UH-60 flown by Chief Warrant Officer Paul Price and Captain Keith Lucas was hit by fire from an M53 at Fort Frederick and crashed on Amber Belair Hill. It would be the first UH-60 shot down in combat, falling on the grounds of the Calabash Hotel and killing Lucas.

Old Maxson

The M53 is similar to the older U.S. M45C MMGM, which was also used extensively in Latin America in the anti-aircraft as well as the ground role. It is known that in 1974, Guatemala was looking to acquire “additional” M55 MMGM systems to protect its airfields, while in 1979 the four M16s in use by the Nicaraguan National Guard engaged guerrillas of the FSLN, who had managed to organize a rebel air force consisting of a Cessna 02-337 and a 402, along with B-50, B-55, Piper Navajo, Piper Aztec, DC-47 and DC-6 models. The Nicaraguan National Guard had an inventory of four M-16 half tracks and some four M45D towed quads. It was reported that at least one M16 was damaged during urban fighting, losing a track, and another was reported prominent at “Loma (steep hill) de Tiscapa,” repelling attacks against Las Mercedes airport (today, Augusto C. Sandino International Airport), the Somoza’s Bunker, the EEBI and the armored battalion, while M45D quad MG batteries deployed to defend El Coyotepe airstrip. Once the National Guard was defeated, the revolutionaries established the FAS-DAA on July 31, 1979, initially equipped with their ZPU-4, three surviving M16s and several M45D mounts, along with M55A2/HS630 and M75 Yugoslavian pieces. The first task of the FAS-DAA was to protect the International Airport and the military facilities of La Casona in Montelimar, so four AAA batteries were established, with the B1001 at Tiscapa, B1002 (internal perimeter) and B1003 (external perimeter) assigned to protect the International Airport and the B1104 in the surroundings of the Managua Country Club.

The M45/M55 is a development of the M33 turret, designed by the W. L. Maxson Corporation of New York in 1941. This turret evolved in the enlarged Maxson M45C in 1942. When mounted on the M20 trailer, the gun was known as the M55 Machine Gun Trailer Mount, and it became the “M16” when mounted on a half-track, and “D” when using its own two-wheeled trailer. It is also noted that in 1944, a number of General Motors CCKW350 2.5-ton 6×6 trucks were equipped with M55 turrets. Anti-aircraft guns proved useful as ground-support arms during the Korean War. However, following tests in 1955, the U.S. Army began to phase out its quadruple machine guns after determining that guns could not provide adequate protection against the expected threat. But then, Vietnam happened …

The M45/M55 would be used extensively by the U.S. Army Transportation Corps in Vietnam. Lieutenant Colonel Phillip N. Smiley, Commander of the 27th Transportation Battalion in Vietnam is credited with directing the assembly of the first two gun trucks, an idea put forward by Lieutenant Colonel Melvin M. Wolfe, executive officer (XO) of the 8th Transportation Group. Under the leadership of Lieutenant Colonel John Burke, the 8th Group borrowed M55 quads to mount on M-35 2.5-ton trucks, in much similar fashion to the mentioned GM CCKW350 trucks of 1944.

At War

In 1981, a dispute exploded between Peru and Ecuador around the possession of three military lookout outposts (PV) called Paquisha (PV-22), Mayaico (PV-3) and Machinaza (PV-4), all three located on the eastern slopes of the Condor mountain range (Cordillera del Cóndor). Hostilities broke out January 22, 1981, when Peruvian recce teams stumbled into the three Ecuadorian detachments camped at old Peruvian observation posts PV-22, PV-3 and PV-4, an area later called “False Paquisha.” Peru dispatched the 13 Jungle Infantry Battalion to recover the area, launching a heliborne operation, the first of its kind in South America, using FAP Mi-8T Hip helicopters from the 3rd Air Group. To the Peruvian commandos’ surprise, an Ecuadoran M55 had been emplaced, but had not been fired, against them and was captured intact. On February 1, 1981, Peru discovered that Ecuador had three other military posts on the northeastern border: PV “El Mirador,” PV-4-A and PV-4-B. By February 19, 1981, Peru had recovered PV-4, where they seized another M55, and the next day they captured PV-4-A and PV-4-B.

Many Latin American countries have made efforts to refurbish the M45/M55 quadruple machine guns and return them back to service. Paraguay retains six operational turrets, and examples are still operational in Ecuador and Colombia. Brazil received considerable equipment during WWII and the post-War period. In 1969, Colonel Oscar de Abreu Paiva, then Commander of the 1st Light Combat Cars Battalion (BCCL – Batalhão de Carros de Combate Leve) borrowed an M3A1 Stuart light tank (vehicle #EB11-487) and replaced the turret with an M55 quad MG from the 5th Anti-Aircraft 90mm Artillery Group (Gcan90 AAe). Around 1982 the Brazilian Lysam Industria e Comercio de Maquinas e Equipamentos developed the M55M, a modernized M45C. The M55M model had a 12-volt electrical system charged by a 5 or 6 hp (3.73 or 4.47kW) Montgomery M-226 or M-252 gasoline engine. Although it retained similar capabilities and performance, traverse speed was improved, and the elevation increased to more than 90° per second to engage fast-crossing targets. This led once more to an effort to match the M55M to the X1A1 light tank, which was a modernized M3A1. The Army completed two anti-aircraft combat vehicle prototypes (XM3D1 and XM3E1), and although successfully tested, the project was canceled, and both prototypes were sent to Restinga da Marambaia Proving Ground.

Colombia found itself fighting a counter-insurgency campaign in the 1980s and 1990s, so it developed the Center for Strategic Road Information and Meteor Companies tasked with keeping the roads open. The Army partnered with the local IMDICOL (Importadora y Distribuidora de Colombia Ltda.) to restore 16 M45C turrets to service, and these were mounted on repowered M8 Greyhound armored vehicles between 1982 and 1984. These vehicles were retired with the signing of the peace agreement with the FARC. However, the M45 can still be refurbished either by the Colombians themselves or passed to a third party, such as El Salvador or Honduras, where they could be updated. A proposed step is to install an M2A1 QCB standard, with a quick-change barrel, fixed headspace and timing and a new flash hider. The original M2 requires setting headspace and timing before firing, after assembly and after required barrel changes. Improper headspace and timing adjustment can cause malfunctions, as U.S. Special Forces vividly experienced in El Salvador during the battle for the Third Brigade in San Miguel in March 1983, and the Fourth Brigade in El Paraiso in September 1988. In San Miguel, a Small Unit Tactical Training (SUTT) from the ODA-7, 3rd Battalion, 7th Special Forces Group fought back an attack on March 25, 1984. In the middle of the battle, an armored tractor was dispatched to support them. As the battle raged, the tractor lumbered into the field, stopped and fired the machine gun. There was only one shot fired because the headspace and timing had not been adjusted on the heavy gun. The crew then implemented a “tactical retreat,” running back inside the base.

The Salvadoran Army never received the M55 quad turret, and they would have loved to have the benefit of the M8/M55. Lacking anything else, they created their own MMGM by mounting M2HB machine guns on armored Woodmaster tractors, much resembling WWI tanks. Perhaps now that the M8/M55 are in excess in Colombia, the Salvadorans could acquire the M8’s chassis to mount the H-90 turret, and the M55 quads could be recycled as fire-support mounts.

With the M2A1, the fixed headspace and timing moves the adjustment task above the operator-level, thereby minimizing the risk of malfunctions or injuries in the field. Another proposition calls for replacing the M2HB machine gun with the GAU-21 (M3P / FN® M3M), which has a 1,100-rounds-per-minute cyclic rate of fire through the use of open-bolt operation and a dual recoil buffer system and a range of nearly 2,000m. An M45C, modified by removing two of the four machine guns and replacing them for two 75mm M20 recoilless rifles, is said to have been tested in 1944 at the Aberdeen Proving Ground, but no other information is available. Following the same logic, the M45C turret can be configured with two M3P or two M2A1 QCB MGs with belt-linked ammunition, an ammo box in the rear and two 90mm M67 recoilless rifles or similar anti-tank weapons replacing the other pair of machine guns to transform it into an interesting and extremely powerful infantry close-support weapon, with limited air and drone defense capabilities.

Mobility can also be improved by mounting the M55 on high-mobility platforms such as the Humvee, the JACAM Unimog Special Forces or the Unimog LRPV variants. Precisely, Ecuador is known to have refurbished several M45Cs and mounted them on Mercedes Unimog and Chevy Silverado trucks. Another Colombian upgrade could match an M55 with the cargo variant of the VLB Bufalo—the Colombian Humvee variant fitted with a mine-protected clearance vehicle (MPCV) capsule. On that note, Peru has done the same, mounting ZPU-2s on Unimog U416 trucks while Lebanese forces mounted ZPU-4s on Unimog U406s; other rebels have mounted the ZPU-2 and M53 on pickup Humvees.

The concept of matching the Maxson turret to an armored, high-mobility, multipurpose, wheeled vehicle (HMMWV) was demonstrated at SOFEX 2016 by the Jordanian defense company KADBB with its mounting a copy of the Maxson M33 turret on the bed of their Al-Washaq 4×4 armored pickup. The Al-Washaq resembles a smaller Humvee, and it is based on a Toyota Hilux chassis, with a 174-horsepower engine coupled to a six-speed gearbox to provide a maximum speed of 100km/h for a range of 600km. The armored shielding is at level B6. The turret swivels 360°, and it is armed with two 12.7x99mm machine guns. The significant positive deflection of weapons is particularly useful in urban areas as in the fight against aerial drones. The turret is clearly inspired in the Maxson M33.

Battle for Culiacan

In October 2019, the city of Culiacan, the capital of Sinaloa, Mexico, found itself under siege. Mexican authorities had arrested two sons of jailed drug kingpin Joaquin “El Chapo” Guzman. Ivan, the elder of them, was quickly freed by his men, who then launched an all-out siege of the entire city in an effort to free his younger brother Ovidio. The drug cartel’s gun trucks drove in, destroying Humvees and civilian cars alike with their M2HB machine guns. As the battled raged for 8 hours, the military scrambled to counterattack. Military-armored M1152 pickups, armed with M45 turrets, could have dispatched them quickly, but the authorities lacked such tools. Mexico received up to 40 M55 gun systems during WWII, but none has been observed in public. If still in storage, the M55s could be refurbished and mounted on either the new Unimog 5000 or Mexico’s new armored M1152 Humvees to make valuable armored support weapons against such targets as the drug cartels’ armored gun trucks. The M1152s armed with the M55, and/or anti-tank weapons, could engage the drug cartels’ “tanks” on their own turfs.