The M65 – Not The Spiral Galaxy, The Atomic Cannon

Operation Upshot-Knothole – 25 May 1953

The M65 Atomic Cannon, often called Atomic Annie, was a towed artillery piece built by the United States and capable of firing a nuclear device. It was developed in the early 1950s, at the beginning of the Cold War, and fielded by 1953 in Europe and Korea.

On May 25, 1953 at 8:30am, the Atomic Cannon was tested at Nevada Test Site (specifically Frenchman Flat) as part of the Upshot-Knothole series of nuclear tests. The test — codenamed Grable — was attended by then Chairman of the Joint Chiefs of Staff Adm. Arthur W. Radford and Secretary of Defense Charles Erwin Wilson; it resulted in the successful detonation of a 15 kt shell (W9 warhead) at a range of 7 miles. This was the first and only nuclear shell to be fired from a cannon.

The Grable mushroom cloud with the Atomic Cannon in the foreground. (Photo courtesy of National Nuclear Security Administration/Nevada Field Office)

After the successful test, there were at least 20 of the cannons manufactured at Watervliet and Watertown Arsenals, at a cost of $800,000 each. They were deployed overseas to Europe and Korea, often continuously shifted around to avoid being detected and targeted by opposing forces. Due to the size of the apparatus, their limited range, the development of nuclear shells compatible with existing artillery pieces (the W48 for the 155mm and the W33 for the 203mm), and the development of rocket and missile based nuclear artillery, the M65 was effectively obsolete soon after it was deployed. However, it remained a prestige weapon and was not retired until 1963.

Of the twenty M65s produced, at least eight survive on display.