3.5-inch Bazooka (M20)

3.5-inch Bazooka (M20)
Name	3.5-inch Bazooka (M20)
Origin	United States
Type	Rocket-propelled grenade launcher
Service	1951–1970s
Used by	United States Army, United States Marine Corps, South Korea, Republic of Vietnam Armed Forces
Wars	Korean War, Vietnam War
Designer	Rocket Branch, Ordnance Corps
Manufacturer	General Electric, Springfield Armory
Weight	11.5 lb (empty)
Length	48 in
Cartridge	3.5 in rocket
Caliber	3.5 in
Action	Single-shot, reloadable

3.5-inch Bazooka (M20)

The 3.5-inch Bazooka (M20) was an American shoulder-fired rocket launcher introduced during the early Cold War era to replace the 2.36-inch Bazooka. It served as an anti-armor and anti-fortification weapon with adoption across United States Army, United States Marine Corps, and allied forces during the Korean War and into the Vietnam War, representing an interim step between World War II infantry anti-tank arms and later guided munitions.

Development and Design

Development began in the late 1940s at the Aberdeen Proving Ground and within the Ordnance Corps to address increasing armor protection on postwar tanks such as the T-34. Designers at the Rock Island Arsenal and contractors including General Electric and Springfield Armory increased projectile diameter to 3.5 inches, integrated a single-piece aluminum tube, and adopted a new backblast mitigation scheme influenced by research at Picatinny Arsenal and tests at Edgewood Arsenal. The design incorporated a percussion firing mechanism derived from experiments conducted during World War II with the M1 Bazooka and lessons from engagements against Panzer IV and Tiger I units; doctrine input came from staff at Fort Benning and planners from the War Department.

Specifications

The M20 measured approximately 48 inches in overall length and weighed about 11.5 pounds empty, accommodating a 3.5-inch diameter rocket with a shaped charge warhead comparable to contemporary anti-tank munitions fielded by British Army and Soviet Army forces. Sights were simple iron assemblies influenced by sights used on the M1 Garand and optical work at Lawrence Livermore National Laboratory-era ballistics studies; effective range was listed near typical assault-weapon engagement envelopes tested at Yuma Proving Ground and Dugway Proving Ground. Ammunition types paralleled developments in shaped charges and high-explosive anti-tank (HEAT) warheads similar to those evaluated by Naval Ordnance Laboratory and allied laboratories in Canada and United Kingdom.

Operational Use

The M20 entered service with U.S. forces during the later stages of the Korean War, where platoons and companies of the 1st Cavalry Division, 25th Infantry Division, and USMC 1st Marine Division employed it alongside recoilless rifles and tank units including the M24 Chaffee and M4 Sherman still in theater. In Vietnam, the launcher equipped infantry and ranger units operating in I Corps and II Corps regions, supplementing M16 rifle-armed squads and coordinating with aviation assets from units like 1st Cavalry Division (Airmobile). Logistic and procurement channels passed through the Ordnance Department and Department of Defense supply chains.

Variants and Modifications

Several field modifications and official variants appeared, including changes to sighting systems influenced by Bailey Controls optics, reinforced launch tubes from contractors such as Colt's Manufacturing Company, and training versions produced for use on ranges at Fort Lewis and Fort Bragg. Ammunition evolution produced high-explosive, practice, and anti-structure rounds paralleling programs at Picatinny Arsenal and industrial partners in New Jersey and Connecticut. Some foreign operators, including Republic of Korea Armed Forces and South Vietnam, adapted locally produced mounts and carriage systems similar to modifications seen in British Army service of analogous weapons.

Combat Performance and Effectiveness

On the battlefield, the M20 offered improved armor penetration relative to the 2.36-inch predecessor, engaging light and medium armored vehicles fielded by North Korean Army and North Vietnamese Army units; however, performance against heavier main battle tanks such as later T-54 variants was limited, mirroring assessments from analysts at RAND Corporation and after-action reports from the 1st Marine Division. Backblast and signature concerns affected employment in urban and jungle environments encountered in Seoul and Hue, and countermeasures by opposing forces, including camouflage and entrenchment tactics noted in Tet Offensive reports, reduced effectiveness. Comparative evaluations by the Infantry School and studies by Office of Naval Research influenced the later shift toward guided anti-tank systems such as the BGM-71 TOW.

Training and Crew Procedures

Crew drills emphasized a two-man team drawn from infantry squads trained at Fort Benning and Camp Pendleton with procedures codified in field manuals prepared by the Department of the Army and training sections of the United States Marine Corps Recruit Depot. Training covered loading, misfire drills, backblast safety measures corroborated by manuals used at Edgewood Arsenal, and integration with squad tactics modeled after doctrine from the Infantry School and combined-arms lessons from Korean War campaigns. Maintenance and ordnance handling were coordinated through unit supply offices and depot facilities such as Anniston Army Depot and Letterkenny Army Depot.

Category:Rocket launchers of the United States Category:Infantry anti-tank weapons