The M65 280 MM Heavy Motorized Gun

The M65 280-mm Motorized Heavy Gun, more commonly referred to as “Atomic Annie”, was the first of a generation of weapon systems designed to fire atomic artillery. The need for the M65 was defined in doctrine following the end of World War II. Specifically, it grew from the planned Ally Invasion of Japan (DOWNFALL) in 1945. Use of small tactical atomic devices were anticipated to be used alongside of standing forces. Following this, deployment of smaller nuclear devices was commonplace for two key reasons. First, it provided a means of deterrence against potential Soviet invasion. Second, it was a way to inflict significant damage to an enemy at a relatively cheap materiel and personnel cost.

When the Cold War began in 1945, atomic devices had not yet been fitted to missiles and bombs were far too heavy for most aircraft. This changed with the deployment of the B-36, B-47, and B-50, but remained an obstacle in closer quarters. Eventually, aircraft, ships, and missiles would be able to launch larger atomic devices, but the function of smaller and tactical atomic weapons fell to short range rockets and artillery. Thus, Atomic Annie found her place.

Based on the “Anzio Annie” gun developed by Nazi Germany (which was already borrowing designs from the Paris Cannon from World War I), the M65 mated multiple pieces into a single weapon system. The T131 280-mm gun was developed at Watervliet Arsenal in New York in 1950 with the intention of arming it with a projectile tipped with a W-9 15 KT warhead (T124). The T72 Gun Carriage was used to cradle the gun. The main prime mover in front of the gun was designated M249, and the one at the rear was designated M250. Both these 4x4 semi-trucks were required to move the gun into firing placement and manufactured by the Kenworth Truck Company. Study on the carriage and recoil mechanism was conducted by the Rock Island Arsenal.

The first test of the gun began in 1952 at Aberdeen Proving Grounds in Maryland. In 1953, the gun was ready to test its atomic delivery capabilities. On 25 MAY 1953, one gun was emplaced in the Nevada Proving Ground as part of the UPSHOT-KNOTHOLE atomic tests. The first and only atomic round fired from these guns was named “Grable”, and it detonated at a range of 8-miles approximately 500 feet above the target.

The gun was subsequently stationed in both the European and Asiatic theaters, seeing most of its time in Germany and Okinawa. However, some of the guns were shipped to South Korea for response testing in the event of ongoing conflict. None of the 20 guns developed and deployed were ever fired in anger. The most these guns saw of any action was firing conventional rounds down-range at firing ranges in Europe near Fulda and over the East China Sea.

Only eight of the guns produced remain today, having been quickly replaced by smaller and more maneuverable weapon systems by 1959. Most display pieces consist of the T131 gun mounted on a T72 carriage. The only complete M65 assembly known to remain is at Aberdeen Proving Grounds.


The Atomic Cannon is a marvel to everyone who has gotten a chance to see her.  Based upon the Anzio Annie, a 283 mm Axis Germany gun, Atomic Annie was a 280 mm monster capable of firing large atomic shells.  She was the first, but not the last.  Upon her retirement in 1963, smaller howitzers and guns took up the mission of using atomic-tipped shells.  This continued until 1992, when all atomic shells were removed from U.S. military inventory.
The T131 gun is only a piece of the entire M65 assembly.  Included in the entire assembly is the T72 carriage along with the M249 and M250 prime movers.  Only one complete system remains, with the rest being just the T131 gun and T72 carriage.

Quick Facts & Specifications (M65)

Weight: 172,865 pounds
Dimensions: 85'0" (L), 10'0" (W), 12'2" (H) (Towed)
Firing Range: Up to 20 miles
Caliber: 280 mm
Yield: 15-20 kilotons (Adjustable)
Crew: 5-7
Variants: T1 (Prototype Gun)
M65 (Production)
Number Built: 20
Origin: United States

Service History & Datelines

25 MAY 1953
The 280-mm gun, known as “Atomic Annie”, fires a nuclear warhead 10,000 yards downrange as 3,200 Soldiers and civilians are on hand to witness the United States’ only nuclear artillery test. The projectile is similar in design and yield (15 kilotons) to the “Little Boy” dropped on Hiroshima. The shot is known as “Grable”, part of the UPSHOT-KNOTHOLE atomic tests.

View History Calendar

Area of Operations


1 Of the three variants, only one was the production 280 mm.  One was the predecessor T1 testbed, while the other was the 175 mm successor.
* The gun is listed as a prototype, however this is loosely the case.  The T1 was the testbed that was used later in 1949 for what became the M65.  It was not part of the same program originally.


  1. There is a doubt that the cannon at Fort Sill is the Atomic Annie. A mix up in the shipping led to Atomic Annie being shipped to Germany and Sad Sack remaining at Fort Sill. Of the six guns 3 at the 867th FA BN and 3 at the 868th FA Bn. is it possible that Atomic Annie could have been one of them?? My assignment was with the 867th 1957-60

    1. Author

      I would have to double check and see what the CMH provenance is with the Atomic Annie at Sill. Cold War weapons systems, I imagine, may have the whole thing thrown out the window when it comes to provenance, but I would certainly have to start there and check. The historians at Sill seem to strongly believe it is the gun, but it also wouldn’t surprise me if it wasn’t. There’s a few items like that in the Army system. I’m currently working on importing an old site full of info on Annie, maybe there’s some reference material there that will be helpful in this case – outside of crossing checking S/N’s.

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