Bootlegging gangsters of the 1920s and 30s firing a barrage of bullets at the G-men in pursuit—that's the mental picture you might have of the Tommy gun. But while the Thompson submachine gun was designed for the trenches of World War I and gained notoriety as a gangster's weapon, it was the battlefields of World War II that saw it win its place in history alongside the other best-known firearms of all time, with as many as two million made.

General Thompson and His Gun

General John Taliaferro Thompson holding the Thompson Sub Machine Gun M192 Wikimedia Commons / DL24

Brigadier General John Taliaferro Thompson, the force behind the Thompson gun, graduated from West Point in 1882. By the outbreak of the Spanish-American War in 1898, Thompson had risen to the rank of lieutenant colonel and was the chief ordnance officer for the campaign in Cuba. After the war he became chief of the Ordnance Department's Small Arms Division, where he was instrumental in selecting the .45 ACP cartridge—the same round his submachine gun would later fire. (The tests involved shooting human cadavers and live cattle to discover which ammunition had the best stopping power. It was a different time.) He also oversaw the development of the Army's new Springfield M1903 rifle and the adoption of the iconic Colt 1911 pistol.

When Thompson retired in November 1914, he took a job as chief design engineer at the Remington Arms Company. WWI had broken out, and Thompson started trying to think of ways to break the horrible, lethal deadlock on the Western Front. He believed mobile firepower was the key and that U.S. troops needed a "trench broom," so in 1916 he started working on automatic weapons.

His company, the Auto-Ordnance Corporation, had its first prototypes ready in 1918. With the help of Theodore Eickhoff and Oscar Payne, Auto-Ordnance continued development of Thompson's idea for a small machine gun "that will fire 50 to 100 rounds, so light that [a soldier] can drag it with him as he crawls on his belly from trench to trench, and wipe out a whole company single-handed."

Faulty Science

Early Thompson gun patent US Patent Office

The Thompson design was based on a scientific principle theorized by Commander John Blish, a former U.S. Navy officer. Blish noticed that when fired with a light load, some of the Navy's breech loading heavy gun had their breech block come unscrewed, while larger loads that produced more pressure held a tighter seal. He attributed this to the different metals used in the breech and breech block. He believed that under great pressure, two different metals could adhere together better than two pieces of the same metal. He called it the Blish Principle, around which he designed a breech block which could be used in small arms. He patented his idea in 1915 and Thompson bought the rights to use the idea in his gun. The Thompson used a small bronze H-shaped block which fitted into the gun's steel bolt. According to the Blish Principle, this would slow the bolt's recoil.

There was just one problem: Scientifically, the Blish Principle of metal adhesion does not exist. In reality, the effect Blish was seeing was that his lock merely added mass to the gun's bolt, which, in a blowback gun, simply slows the travel of the bolt. People figured this out during World War II, and British troops using Thompsons frequently removed the Blish lock. Later, when the Thompson was simplified to create the M1, the Blish lock was also abandoned.

With the Blish lock simply adding mass, the Thompson functioned as a simple blowback like many other contemporary submachine guns including the STEN, MP40, and Soviet PPSh-41. When the trigger was pulled, the bolt was released, slamming into the breech. That ignited the round in the chamber and fired the gun. The pressure from the fired round would then send the Thompson's bolt recoiling to the rear, extracting and ejecting the spent case before the process repeated itself.

From the Western Front to the Silver Screen

A Thompson Gun and a pair of Colt .45 pistols Hulton Archive Getty Images

Thompson himself was recalled to service when the U.S. entered the First World War in 1917, he was promoted to Brigadier General and served as the director of arsenals throughout the war. The early Thompson prototypes came too late to fight the war they'd been designed for, but they had suitably aggressive names Persuader and Annihilator. One early model capable of firing up to 1,500 rounds per minute—an utterly uncontrollable rate of fire. In 1919, the Thompson began to take on its famous classic shape, and by 1921, Auto-Ordnance had a refined its submachine gun to the point it was ready to go to market.

With the great war over, Thompson took his gun to the civilian market, selling it as an "anti-bandit gun." Thompson travelled tirelessly to promote and publicize his gun and its capabilities. In 1921, he embarked on a sales tour of Europe. The British came away impressed by the submachine gun, praising it for being handy and compact. But post-war budget constraints prevented any purchases. In 1927, Thompson tried again, demonstrating an improved model to the French army, who was unimpressed. The Thompson did find some customers with the U.S. Postal Service ordering 200 to protect the mail from violent thieves.

Of course, that's not the end of the story. The Thompson's high rate of fire and large magazine capacity saw it catapulted to infamy as the weapon of choice for lawmen and gangsters during the 1920s and 30s. Thompsons quickly entered the vernacular of popular culture as Tommy Guns or Chicago Typewriters. Two were used during the infamous St. Valentine's Day massacre when 70 rounds (a full 20-round box magazine and a 50-round drum magazine) were emptied into seven members of the Moran Gang in a matter of seconds. The likes of John Dillinger, Baby Face Nelson, the Barker gang, and Pretty Boy Floyd all used Tommy Guns. And while the Thompson was also found in the hands of the law, it has become forever associated with Depression-era gangsters. (Although some police departments had privately bought Thompsons it was not until 1935, that the FBI finally received 115 Thompsons in custom carrying cases. Ironically by then the majority of gang members and gangsters the FBI had been tasked with stopping had already been either killed or captured.)

Lieutenant Chief William Shoemacher aiming a Thompson machine gun, Chicago, Illinois, 1926. Chicago History Museum Getty Images

The movies did their part in this myth-making. During the burgeoning years of Hollywood, the Tommy Gun became extremely popular on the silver screen, with popular gangster films featuring charismatic outlaws wielding the Thompson. By 1935, however, a set of guidelines called the Motion Picture Production Code had been introduced. In an effort to deglamourise outlaws, the code dictated that gangster films should be filmed from the G-Men's perspective. Gangsters could no longer be seen with automatic weapons and the Tommy Gun became the on-screen weapon of the FBI agent. This altered the tone of gangster films with the Tommy guns iconic status helping to glamorise the G-men rather than the gangsters. The Thompson has since appeared in more than a thousand films and TV shows.

Back to Europe

Despite the notoriety, business wasn't good. The Thompson had the dubious honor of being one of the first weapons subject to the 1934 National Firearms Act, which prohibited the use of automatic and concealable weapons by civilians in the U.S. Without large scale military contracts, Thompson's company struggled. Only small batches of his submachine guns were purchased by the US Marine Corps for use overseas. And so, despite decent civilian sales, Auto-Ordnance was on the brink of liquidation by 1929. The company was in a massive $2,200,000 hole of debt.

And then, World War II broke out.

In 1939, the full outbreak of war in Europe, Time magazine described the Thompson as "The deadliest weapon, pound for pound, ever devised by man." General Thompson's gun was about to face its greatest challenge. After the Fall of France in June 1940, Britain needed every weapon the could get and placed an open order for Thompson submachine guns. By April 1942, 100,000 Thompsons had arrived in Britain. They became a favorite of the newly formed elite Commando units who used them in raids on occupied Europe. The US military formally adopted the Thompson in September 1938, but did not order any guns until the summer of 1939. But by February 1942, half a million Thompsons had been made.

A Marine named Sgt. John Wisbur Bartlett Sr. of the 1st Marine Division draws a bead on a Japanese sniper with his tommy-gun as his companion ducks for cover. The division is working to take Wana Ridge before the town of Shuri. Okinawa, 1945. U.S. Marine Corps

The simplified Thompson M1 and later M1A1 would arm troops fighting in every theatre of operations from the Pacific to North Africa to Europe. This was the final realization of General Thompson's dream of equipping American troops with a small machine gun capable of delivering devastating firepower. Thompson himself, though, did not live to see his weapon become a key part of the Allies' arsenal as he died in June 1940. But his weapon soldiered on and saw service in Korea and Vietnam before it was finally retired from the U.S. military.

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