It is not my intention here to go into  the fascinating history of the Thompson sub-machine gun, suffice to say that Ireland played a critical role in the conception and invention of this amazing weapon.


For the financial backing came from Thomas Fortune Ryan, an Irishman who knew a good thing when he saw it. He was also a funder of Clan na Gael and knew all about the Irish struggle back home and how the hard pressed IRA needed all the weapons they could get. America was traditionally the arms smuggling route for weapons.

General Thompson himself travelled to Europe in May 1921 and trialled the new Thompson gun for the British Army on 30th June at the Royal Small Arms factory at Enfield. Probably because of the press attention being paid to the East Side seizure of arms for Ireland, their interest waned.


The first customer for the gun was the Irish Republican Army (IRA)  and they paid cash for large numbers of guns.

Harry Boland, senior IRA emissary who arrived in America in 1919 had been tasked with meeting Ryan.


When Governments, police and military were doubtful of the Thompson gun, it was the Irish who realized its value and worth.


The  gun was designed by Colonel John Thompson in 1919. He originally wanted to design an automatic battle rifle but soon looked at the idea of a  small hand held machine gun, which was revolutionary for its time.

General Thompson at the time was well known in arms circles – he was Director of Small Arms development for the US Ordnance dept.

He formed a company called Auto-Ordnance Corporation with Ryan in December 1916. He was later to bring his son Marcellus onto the board.

His idea was to use the commonly available .45ACP round (Automatic Colt Pistol) which had been used in the famous Colt 1911 automatic pistol. It was a heavy man stopper round. The US military at the time was used to the .30 calibre.

He had the description of  “trench broom” in mind as the war was still progressing.

His first prototype was known as the “Persuader” which was ready just as World War 1 ended. In design stage they used a webbing belt to feed the cartridges but the mechanism would jam.

Next came the 20 round box magazine which progressed to the iconic 50 round and 100 round round drum.


The nest design was known as the “Annihilator 1”

There was a debate at this stage on what they should call the invention. General Thompson objected to calling the piece a “machine gun” so the term “sub-machine gun” was adopted to indicate that it was of a lower category than a rifle cartridge machine gun.. The question however remained as to whose name the invention should take,

The General proposed to name it “The Ryan Sub-Machine Gun” after their financial backer Fortune Ryan but he did not agree and insisted that it be christened “The Thomspon Sub-Machine Gun” as he was the military man.


The prestigious Colt Firearms Company was to manufacture the Thompson Gun. Colt saw that they had and offered $1 for all rights. Ryan told Thompson to refuse. The production deal was signed on August 18, 1920. Colt were contracted to manufacture 15000 units in the first year with 20 round box magazines which they did. The cost to manufacture one unit was $44.56. Last minute changes to the design included sights, butt stock and semi-automatic features. The first Colt Thompson came off the line in April 1921 and was aptly called “Model of 1921” and bore these words on the frame with four serial numbers (first 1000 units) on receiver left hand side, under forearm of grip, the frame and on barrel chamber. The actuator slot on top of frame is squared in early models and rounded in later. Later serial numbers were dropped from barrel location.


The wooden butt stocks were made by Remington as well as the barrel blanks. The Remington trademark of an anchor is visible on the stocks. The drum magazines were stamped by an outside house and assembled and blued by Colt. The rear sights were made by Lyman Company.


The first Colt production Model of 1921A had a rate of fire of 800 rounds  a minute.


Magazines ranged from the standard 20 round box  known as XX, to 30 round box known as XXX, 18 round (shot shell) box, Type L 50 round drum and Type C 100 round drum.

The Model of 1921 Thompson weighed 10lbs 4ozs.


The stick magazine weighed 2lbs loaded.

A 50 round drum magazine (L denotation) weighed 2lbs 8ozs.

A 100 round drum magazine (C denotation) weighed 3lbs 2 ozs.


Colt first production model serial number 41 was shipped at end March 1921 and last of the contract serial number 15040 manufactured in July 1922.

These first 15000 guns lasted Auto-Ordnance for almost 20 years.

By 1939, some 4750 Model of 1921 guns were still in storage. Auto-Ordnance had sold only 1500 to the US Government, 4700 sold elsewhere in the US with another 4100 sold abroad. In November 1939, and order for 3000 guns was placed for Models of 1921 by the French Government. This order was fulfilled in February 1940.


The logos used on the Colt guns was of two distinct types – the early one was “Auto-Ordnance Co.” in a bullet image on Model of 1919 prototypes made by Auto-Ordnance themselves and then Model of 1921 guns made by Colt up to serial number 1000. After that, the Thompson bullet image was used on the remaining 14000 guns and all guns thereafter.


Interstingly, on 17th May 1921 a purchase of two guns serial numbers 397 and 411 was made and recorded in the name of “Thos. F. Ryan” – the financier behind Auto-Ordnance himself had succumbed to owning the Thompson Gun.


Thomas Fortune Ryan died in 1928 , Marcellus Thompson died in 1939 and General Thompson died in 1940.