Thompson Submachine Gun

The Thompson submachine gun — known variously as the:

• "Tommy gun"
• "Chicago Typewriter"
• "Chicago Organ Grinder"
• "trench broom"

— is a blowback-operated, selective-fire submachine gun chambered in .45 ACP. Invented by Brigadier General John T. Thompson of the U.S. Army, it was designed between 1917 and 1920 with the explicit purpose of breaking the stalemate of World War I trench warfare. It arrived too late for that war, became infamous in peacetime, and then proved indispensable in the next one.

According to Wikipedia, the Thompson is the first weapon to be labeled and marketed as a "submachine gun" — a term Thompson himself coined. It entered production in 1921 and remained in continuous manufacture through 1945, with approximately 1.75 million produced across all variants. Semi-automatic civilian versions remain in production today under the Auto-Ordnance name.

The Thompson's historical footprint is outsized even by the standards of iconic firearms. It helped provoke America's first major federal gun control legislation. It was adopted by gangsters, lawmen, IRA volunteers, U.S. Marines, Allied paratroopers, Chinese warlords, and Viet Cong guerrillas. It appeared on both sides of nearly every significant conflict between 1921 and the 1990s. Few American-made weapons have cut a wider path through history.

Early Development (1914-1920)

John Taliaferro Thompson came to the submachine gun by a roundabout route. A West Point graduate and veteran of the Spanish-American War, he spent most of his military career in the Army's Ordnance Department. According to the Beaches of Normandy source, he directed ammunition supply to U.S. forces in Cuba during the Spanish-American War and arranged for Gatling guns to be deployed at the Battle of San Juan Hill.

He later supervised development of both the M1903 Springfield rifle and the M1911 pistol — conducting ballistics tests on beef cattle, per Coffee or Die, to help determine the best pistol cartridge for the U.S. Army.

Thompson retired from the Army in 1914, worked briefly for Remington Arms, and then founded the Auto-Ordnance Company in 1916 with financial backing from businessman Thomas F. Ryan. The company had one goal: an automatic weapon capable of clearing enemy trenches. Thompson envisioned a "one-man, hand-held machine gun" — a weapon with a high rate of fire that didn't need range or accuracy, because inside a trench you were never going to shoot very far anyway.

While working through the engineering challenges, Thompson came across a patent filed in 1915 by U.S. Navy Commander John Bell Blish. Blish had observed that two dissimilar metals pressed together under extreme force — such as the explosion of a cartridge — exhibited greater friction than normally expected. Thompson incorporated this Blish lock into his design as a friction-delayed mechanism to regulate the weapon's automatic fire.

According to Wikipedia, principal designers Theodore H. Eickhoff, Oscar V. Payne, and George E. Goll carried out the primary development work in Cleveland, Ohio. By late 1917, the limits of the Blish lock became apparent — it functioned essentially as an extreme manifestation of static friction and couldn't serve as a true locked-breech system. Rather than scrap the design, the team reconfigured it to work as a friction-delayed blowback action. The only cartridge in service suitable for this arrangement was the .45 ACP.

Two prototype configurations were considered: the belt-fed Persuader, which was partially built but never completed, and the magazine-fed Annihilator, which became the direct ancestor of the production Thompson.

Most design issues were resolved by 1918. The prototypes were ready to ship to Europe. The war ended two days before they could.

At an Auto-Ordnance board meeting in 1919, with no war left to fight, the weapon was officially renamed the "Thompson Submachine Gun" — coining the term that would define an entire category of firearms. The German MP 18, developed concurrently and fielded earlier, is recognized as the world's first submachine gun by design, but Thompson's was the first to actually carry the "submachine gun" label in its marketing.

Production Models and Wartime Evolution

The first major production model, the Model 1921, was manufactured by Colt for Auto-Ordnance in a run of 15,000 units. It was a finely finished weapon — blued, finned barrel, adjustable rear sight, quality wood furniture — and priced accordingly at $200 per unit, roughly equivalent to $3,610 in 2025 dollars according to Wikipedia. At that price point, in peacetime, it sold poorly.

In 1927, the U.S. Navy ordered 500 Thompsons but demanded a lower rate of fire. Oscar Payne replaced the actuator with a heavier one and stiffened the recoil spring, reducing the cyclic rate from 800 rpm to 600 rpm. This became the Model 1928 — the last U.S. Army small arm to use a year designation in its official nomenclature, and the version that would enter World War II as the primary military Thompson.

As war loomed in Europe, Auto-Ordnance was struggling. Thomas Ryan, the company's primary investor, had died in 1928. Sales had lagged through the Depression years. The company contracted Savage Arms to manufacture the M1928A1 at scale — and most of the WWII-era Thompsons were Savage-built, though the Savage name appeared nowhere on the guns due to contractual restrictions, per the Beaches of Normandy source.

The wartime simplification program produced the M1 in April 1942 and the definitive M1A1 in October 1942. The Blish lock was eliminated entirely. The Cutts compensator, barrel cooling fins, drum magazine compatibility, and removable stock all disappeared. The charging handle moved from the top to the side. A fixed rear sight replaced the adjustable Lyman. The result was a weapon that could be produced in half the time of the M1928A1, at a fraction of the cost. Between 1939 and February 1944, the per-unit price dropped from $209 to $45, including accessories and spare parts.

Operating Mechanism

The Thompson fires from the open-bolt position — the bolt is held fully rearward by the sear when cocked, and when the trigger is depressed, it travels forward to chamber and fire simultaneously. This eliminates the risk of cook-off that can occur in closed-bolt automatic weapons. The action is selective-fire, capable of both semi-automatic and fully automatic fire.

Thompson submachine gun firing cycle showing the difference between Blish lock and straight blowback operation

The M1928A1 weighs 10.8 lb empty; the M1A1 comes in at 10 lb. Both figures put it in roughly the same weight class as the M1 Garand rifle — which, for a submachine gun, is heavy. That weight was a persistent complaint throughout the weapon's service life, and it contributed directly to its replacement in several theaters.

The barrel measures 10.52 inches on standard models, or 12 inches with the Cutts compensator attached. Effective firing range is approximately 164 yards (150 meters), though in practice the .45 ACP bullet loses reliability against cover well before that. Muzzle velocity runs 935 feet per second.

Magazine Systems

Magazine options evolved considerably over the gun's production life. The original Model 1921 came with a 20-round "stick" magazine and was compatible with 50-round and 100-round drum magazines. The drums provided significant firepower on paper, but British forces in North Africa criticized their excessive weight, their tendency to rattle during movement, and the complicated procedure required to attach, detach, and reload them. Reloading an empty 50-round drum required inserting all 50 rounds and then winding the mechanism until at least 9 to 11 audible clicks were heard. By contrast, the box magazine could be inserted with the bolt closed, dropped out cleanly for malfunction clearing, and refilled with loose rounds in the field.

Two extended magazine options were tested at Fort Knox on December 6, 1941 — a 30-round box and a welded double-20 configuration. Both were judged superior to the existing options, and the 30-round box was approved as the new standard that same month. The M1 and M1A1 were designed around box magazines only and cannot accept drums.

The Thompson was among the earliest submachine guns to incorporate a double-column, staggered-feed box magazine design. According to Wikipedia, this contributed substantially to its reputation for reliability under field conditions, and the weapon performed better than most after exposure to rain, dirt, and mud — though African sand proved troublesome enough that British armorers in North Africa field-modified their guns by removing the Blish lock entirely.

The Model 1919 prototypes had cyclic rates as high as 1,500 rpm. Production Model 1921s ran around 800 rpm. The M1928 and later models settled at 600–725 rpm. The high rate of fire on early models, combined with a heavy trigger pull and a stock with excessive drop, made the barrel climb off target quickly in automatic fire.

Early Combat Use (1921–1934)

The Thompson first saw combat not in a foreign war but in the coalfields of West Virginia. According to Wikipedia, on June 13, 1921, state troopers fired Thompsons at striking miners near Lick Creek. By the time of the Battle of Blair Mountain later that year, 37 Thompsons were in the hands of the West Virginia state police and 56 more were held by coal companies and local enforcement.

Almost simultaneously, agents of the Irish Republican Army — notably Irish gunman Harry Boland — were purchasing Thompsons in the United States. IRA commander Tom Barry of the West Cork Brigade conducted the first test of the weapon in Ireland in the presence of IRA leader Michael Collins. The IRA purchased a total of 653 units, though U.S. customs seized 495 of them in New York in June 1921. The remainder reached Ireland via Liverpool and saw use in the final month of the Irish War of Independence. According to Wikipedia, the Thompson was not found to be particularly effective in Ireland — it caused serious casualties in only 32 percent of the incidents in which it was used. Additional imports after the July 1921 ceasefire were used during the subsequent Irish Civil War.

The gun's Irish connection would prove remarkably durable. During the Troubles (1969–1998), historian Peter Hart documents that the Thompson remained a key part of both the Official IRA and Provisional IRA arsenals well into the 1970s, when it was finally superseded by the Armalite and the AK-47.

The Thompson's domestic notoriety grew through the 1920s in direct proportion to its adoption by organized crime. According to Coffee or Die, Irish hitman Frank McErlane — described as one of Al Capone's most ruthless associates — introduced the Thompson to Chicago's criminal underworld. The weapon's saturation of that city gave it the nicknames that stuck: "Tommy Gun," "Chicago Typewriter," "Chicago Organ Grinder," and "Chopper."

The St. Valentine's Day Massacre on February 14, 1929, cemented the Thompson's reputation permanently. Seven members of Bugs Moran's North Side gang were killed in a Chicago garage — an event so visually iconic that it defined the Thompson's public image for generations. According to All That's Interesting, the actual number of rounds fired was approximately 70, not the "thousands" that legend suggested.

Gangsters appreciated specific features beyond raw firepower. By removing the buttstock and swapping the drum for a 20-round stick magazine, the gun could be concealed under an overcoat. Notable users included:

• George "Machine Gun" Kelly
• Pretty Boy Floyd
• Baby Face Nelson
• John Dillinger

Dillinger famously posed for a photograph with his Thompson in 1934.

The public backlash was significant. The perceived connection between submachine guns and organized crime violence was, according to Wikipedia, one of the primary justifications offered for the National Firearms Act of 1934 — which required all owners of fully automatic firearms to register their weapons with what would eventually become the ATF, and placed restrictions on the possession, transfer, and transport of such weapons.

John Thompson himself was troubled by this history. According to All That's Interesting, before his death in 1940, he wrote:

"I have given my valedictory to arms, as I want to pay more attention now to saving human life than destroying it... It has worried me that the gun has been so stolen by evil men & used for purposes outside our motto, 'On the side of law & order.'"

He died before seeing his invention deployed in World War II.

The U.S. Postal Inspection Service, tasked with protecting mail from a surge of armed robberies, purchased approximately 200 Model 1921 Thompsons in 1926. These weapons were loaned to the U.S. Marine Corps, which was then guarding mail shipments — prompting the Navy to formally evaluate the Thompson. That evaluation led directly to the Model 1928 order.

In Nicaragua and elsewhere during the Banana Wars, the Thompson proved effective as a point-defense weapon against guerrilla ambushes. According to Wikipedia, its use there led directly to the creation of four-man fire teams that could generate as much firepower as a nine-man rifle squad — a doctrinal innovation with lasting implications for small-unit tactics.

World War II Service

The Thompson was formally adopted by the U.S. military in 1938. When the war came, it found its natural element — not in open-field engagements, but in the close terrain where its limited range and massive short-range stopping power were assets rather than liabilities.

In the European theater, the Thompson was issued most heavily to:

• Scouts and patrol leaders
• Non-commissioned officers
• Commissioned officers
• Tank crewmen
• Raiding parties and paratroopers

British and Canadian commando units, U.S. Army Rangers, and paratroopers used it frequently. Paratroopers were known to "borrow" Thompsons from mortar crews before patrols behind enemy lines. According to Coffee or Die, 1st Sergeant Leonard Funk Jr., a U.S. Army paratrooper, used his Thompson during the Battle of the Bulge in a January 29, 1945 engagement near Holzheim, Belgium — emptying a 30-round magazine into a group of more than 80 German soldiers who had ordered his unit to surrender. He was awarded the Medal of Honor.

The Thompson was widely distributed through Lend-Lease. The Soviet Union received M1928A1s, often included as standard equipment with Lend-Lease light tanks, though a shortage of .45 ACP ammunition limited their use. Britain, France, China, and others received substantial quantities.

In the Pacific and Asian theaters, the picture was more complicated. The Thompson saw heavy use during the Kokoda Track campaign in New Guinea in 1942, where it was the only submachine gun available to Australian forces and became so valued that soldiers picked up guns dropped by fallen comrades. However, the weapon's weight and the difficulty of supplying .45 ACP ammunition eventually led Australian units to replace it with Australian-made submachine guns — the Owen and the Austen — in 1943. British forces in Burma largely replaced it with the Sten gun. New Zealand commandos in the Solomon Islands and Guadalcanal campaigns similarly switched to the lighter Owen.

The Thompson's fundamental limitation in heavy jungle cover was that the low-velocity .45 ACP bullet would not reliably penetrate small-diameter trees or armored vests. U.S. Army jungle patrols that had initially deployed with Thompsons progressively shifted to the Browning Automatic Rifle, whose higher-powered rounds didn't share this problem.

The Army introduced the M3 "Grease Gun" in 1943 with the explicit intention of replacing the Thompson. The M3 was considerably cheaper to produce. But unforeseen production delays and modification requests kept Thompson purchases going until February 1944. At war's end, the Thompson outnumbered M3/M3A1 submachine guns in service by nearly three to one — over 1.5 million military Thompsons produced during the war alone.

Post-War Conflicts

The Thompson's post-1945 career was extensive. It was used by both sides in the 1948 Arab-Israeli War, the Greek Civil War, the Korean War, the Cuban Revolution, and the Bay of Pigs Invasion. During the Korean War, U.S. troops were surprised to encounter Chinese communist forces armed with Thompsons — weapons that had previously been supplied to Nationalist Chinese forces before the fall of Chiang Kai-shek's government in 1949. Many of those captured Chinese-carried Thompsons were subsequently pressed into service by American soldiers and Marines.

The Yugoslav Army received 34,000 M1A1 Thompsons during the 1950s as part of a U.S. military aid agreement. Those guns were still turning up in service during the Yugoslav Wars in the 1990s. In Vietnam, some South Vietnamese units and reconnaissance elements used Thompsons; the Viet Cong both captured existing examples and manufactured their own copies in jungle workshops. The FBI used Thompsons until they were declared obsolete and ordered destroyed in the early 1970s. A U.S. Army Special Forces soldier interviewed by Coffee or Die described keeping six Thompsons locked, loaded, and ready for base defense at a camp in Vietnam in 1963 — valued specifically for the .45 caliber's knockdown power at close range.

Legal and Regulatory Impact

The Thompson's most direct institutional legacy is the National Firearms Act of 1934. The gun's visibility in organized crime violence during Prohibition created the political conditions for the first major federal firearms regulation in American history. Every subsequent layer of federal automatic weapons law traces back, at least in part, to the Thompson's notoriety.

Doctrinal influence is harder to measure but equally real. The Thompson's performance during the Banana Wars contributed to the development of four-man fire teams as a standard small-unit structure — a concept that persisted in U.S. military doctrine long after the Thompson itself was gone. Its widespread issue to scouts, NCOs, and patrol leaders across multiple armies helped establish the submachine gun as a standard component of infantry unit organization, rather than a specialty weapon.

The Thompson was also the first weapon to carry the "submachine gun" designation in its marketing — the category name itself is a Thompson invention. Every submachine gun that followed, from the MP5 to the UMP, carries that label in part because of the 1919 Auto-Ordnance board meeting where Thompson's team decided they needed something to call it.

Cultural and Collector Significance

As a collector's item, the Thompson commands substantial prices. According to Wikipedia, as of 2024, original Colt Model 1921 and 1928 Navy machine guns have sold for $25,000 to $45,000 or more. A Model 1921A with a claimed — but undocumented — provenance to Bonnie and Clyde sold at auction in Kansas City on January 21, 2012, for $130,000.

Semi-automatic civilian versions remain in production by Auto-Ordnance (now a subsidiary of Kahr Arms). The Model 1927A1 — a closed-bolt, 16.5-inch barrel rifle under federal law — has been produced since 1974, currently from Worcester, Massachusetts. These are legally rifles, not NFA items, due to their closed-bolt operation and barrel length. The fully automatic selective-fire originals are no longer manufactured, though transferable pre-1986 examples remain legal under the NFA for registered owners.

In Canada, all Thompson variants — including semi-automatic versions — are prohibited by name under Prohibited Weapons Order No. 13 from 1995. In the United Kingdom, any centerfire semi-automatic conversion or purpose-built semi-automatic Thompson is prohibited under the Firearms Act 1988. Full-auto versions have been prohibited since the Firearms Act 1968.

The Thompson's cultural reach extends well beyond its mechanical specifications. Winston Churchill's famous 1940 photograph holding a drum-magazine Thompson was used in Nazi propaganda to characterize the British Prime Minister as wielding a gangster's weapon. The image backfired — or depending on your point of view, worked exactly as intended. The Thompson's association with both lawmen and criminals, with Prohibition Chicago and the beaches of Normandy, made it one of the most symbolically loaded firearms in American history.

The Thompson is one of those guns where the historical weight almost obscures the mechanical reality. Strip away the mythology and what you have is a well-made but heavy, expensive, short-ranged submachine gun that was probably more useful as a psychological weapon than a tactical one for much of its career. The drum magazines were a liability almost everywhere they were used. The .45 ACP couldn't punch through jungle cover. The weight was a legitimate complaint from Australia to Burma to Vietnam.

And yet — it kept showing up. Decade after decade, conflict after conflict, on every side of every fight. That persistence isn't really about the gun's mechanical virtues. It's about what the Thompson represented: high-volume automatic fire in a package one person could carry.

The Thompson proved the concept of portable automatic fire. Everything that came after — the Sten, the MP40, the M3, the Uzi, the MP5 — is downstream of the argument the Thompson won.

The legal legacy is the part that deserves more attention than it usually gets. The NFA of 1934 happened largely because of this gun. That legislation shaped federal firearms law for the next 90-plus years. You cannot understand American gun law without understanding the Thompson's role in creating the political conditions for it. Whether you think the NFA was a reasonable response or an overreach, the Thompson is why the conversation happened when it did.

For collectors, the original transferable automatics are serious money and genuinely scarce. The semi-auto versions from Kahr/Auto-Ordnance are fun range guns with a lot of history behind them — just don't expect them to shoot like the originals, because the closed-bolt design and 16.5-inch barrel are not the same animal. They look the part, which for most buyers is probably the point.

• Wikipedia: Thompson submachine gun — https://en.wikipedia.org/wiki/Thompson_submachine_gun
• Coffee or Die: Gangsters, G-Men, and Green Berets: A Look at the Tommy Gun — https://www.coffeeordie.com/article/tommy-gun
• Britannica: Thompson submachine gun — https://www.britannica.com/technology/Thompson-submachine-gun
• Beaches of Normandy Tours: The Thompson submachine gun — https://www.beachesofnormandy.com/articles/The_Thompson_submachine_gun/?id=9a420f9b2b
• All That's Interesting: Tommy Gun: The Infamous Weapon That 'Made The '20s Roar' — https://allthatsinteresting.com/tommy-gun

Last Updated: February 27, 2026