The United States Government had a problem keeping its European allies calm during the Cold War when a Russian blitzkrieg threatened with tens of thousands of tanks rolling across Europe at will. The need was for a small tactical nuclear weapon that could be used as a deterrent to Russia and ease America's European allies at the same time. The project was assigned in 1949 to one man - Robert Schwartz - who began working on the design at the Pentagon, sequestered in a guard-watched, locked room for 15 days. During that time, the weapon began to take shape and shortly the project was transferred to the Picatinny Arsenal in New Jersey. Picatinney Arsenal had been given the mission to develop the artillery shell for the weapon, one that could sport a nuclear payload. Again Schwartz was locked away to finalize the model of the cannon and its mode of transport. Different strategies were considered, from a towed platform to the cannon being self-propelled. The next step was to sell the project to the Pentagon. This fell to the chief of the R&D section at Picatinny - Samuel Feltman - who eventually pushed the project through. Once the contract was signed, Schwartz was made the project manager and with a selected team completed the program of an Atomic Cannon in three years, this occurring in 1952 at a cost of $800,000. She was more than 80 feet in length - the largest mobile artillery piece ever built.
Schwartz settled on a combination of the two modes (towed and self-propelled). It resembled a large fire engine with two 375 horsepower tractors with one positioned at each end. The two-tractor system was capable of independent steering with both tractors facing in opposite directions while the drivers had communication with a newly designed phone system. This towed arrangement could make sweeping right turns and could travel at 35 miles per hour on paved or gravel roads with a 28 foot width. The tractors on both ends would back the system into firing position. The completely hydraulic design had no electronics and the M65 was semi-mobile, taking some 15 minutes to be set up to fire - this accomplished using hydraulic jacks and winches. The cannon itself was balanced on its 9 foot circular base plate with jacks. The firing crew of 5 to 7 men was able to move the gun a full 360 degrees and load the 600lb shells by a hydraulic rammer into the breech. If required, gears were a back up should enemy fire damage the hydraulic system. The recoil of firing a 600lb shell was absorbed by dual recoil buffers, one separated the barrel from the upper carriage and the second between the upper and lower carriages.
On January 20 1953 Eisenhower became President of the United States. In the inaugural parade were 65 bands, 50 state floats with 5,000 private citizens, 22,000 service men and women, 350 horses, 3 elephants, an Alaskan dog team and one M65 atomic cannon - no doubt a reminder to the Soviets and the Chinese. On May 25th 1953, the Atomic Cannon was fired and detonated a 15kt shell with a W9 warhead at a distance of 6.2 miles at the Nevada test site under the codename "Grable". This was the only nuclear warhead ever fired from an artillery piece. As the Korean War continued, the rumor that an atomic cannon able to fire a 15kt W9 nuclear warhead might be deployed on the Korean Peninsula helped usher in the end of the war.
A total of twenty M65 systems were produced with about 10 to 16 deployed, many of these across Europe in 1957. Throughout the 1950s, the M65's were often moved in the forests to keep the Soviets guessing on their placements. The M65 is the strangest weapon the ordnance corps produced though the cannon provided an important deterrence role in the tactical nuclear arsenal of continental Europe. The troops called her "Atomic Annie" after "Anzio Annie" the K5 gun used by the Germans in Italy. The M65 was retired in 1963 and 8 are on display at military museums.