During the early Cold War era, military invention accelerated as America and the Soviet Union competed to develop nuclear weapons that would transform the battlefield. Both countries sought to integrate atomic power with traditional forces, and for the U.S. Army, it gave birth to an incredible project: a nuclear-armed artillery piece. From this endeavor was born the M65, better known as “Atomic Annie”—a device that came to serve as an emblem of Cold War boldness, but found itself more a technological fascination than a practical answer.
The tale of Atomic Annie starts in the immediate aftermath of World War II, when American engineers studied the German Krupp K5 railway guns that Allied forces had dubbed “Anzio Annie.” The question in the middle was bold: could the frightening, destructive force of atomic bombs, used to conclude the Pacific War, be modified for deployment by ground troops on the battlefield?
Picatinny Arsenal in New Jersey accepted the challenge, led by engineer Robert Schwartz, in designing a behemoth of an artillery weapon. His team copied extensively from the German guns but emphasized road mobility instead of using railway tracks.
The result was the M65, a real engineering wonder of its time. Measuring 85 feet long and weighing over 170,000 pounds, it required two specially built tractors to move and a crew of up to seven soldiers to operate. Its 280mm barrel could fire a nuclear shell up to 20 miles, and despite its immense size, the gun could be made ready to fire or move in under 30 minutes—a feat that was unprecedented at the time.
Mounted on a ball-and-socket joint, the gun did not have much horizontal mobility, and its mere presence commanded attention wherever it went. A prototype even made an appearance in President Dwight D. Eisenhower’s first inaugural parade in January 1953, demonstrating the pace at which the project had progressed.
The most storied moment for Atomic Annie occurred on May 25, 1953, at the Nevada Test Site during Operation Upshot-Knothole. The nuclear shell, named “Shot Grable,” was the sole atomic round ever to be discharged from a cannon. Fort Sill, Oklahoma, soldiers loaded an 11-inch, 800-pound W9 shell into Annie’s barrel. At 8:30 a.m., the cannon fired, sending the shell on a 19-second journey before exploding in an airburst six miles away with a yield of 15 kilotons—comparable to the Hiroshima bomb.
Thousands of troops, scientists, and administrators observed the test and took part in a series of drills to test how troops and equipment would survive a nuclear explosion. The explosion created a typical mushroom cloud and an unusual precursor shock wave, inflicting visible damage on surrounding vehicles and buildings. The test did demonstrate that nuclear artillery was possible, but it was the only time the U.S. ever fired a live atomic shell out of a cannon.
After the successful trial, the Army bought about 20 M65 cannons for around $800,000 apiece—a huge sum at that time. They were stationed throughout Europe, Korea, and Okinawa, usually shifted so as not to be targeted by the enemy. Their period of service was brief, however.
Soon afterward, warhead miniaturization pushed to new limits made possible the use of atomic shells in regular 155mm and 203mm artillery, and tactical missiles soon made the massive M65 obsolete. By 1963, merely a decade after its dazzling debut, Atomic Annie had been retired.
The history of the M65 also featured a few offbeat anecdotes. In Cold War deployments, the original test gun and alternate, officially known as “Alternate,” but often referred to as “Sad Sack,” got mixed up by accident—a switch that went undetected for a decade until the tenth anniversary of Shot Grable. The original “AWOL Annie” was finally found in Germany and brought back to Fort Sill, where it remains a museum display, along with a few other M65s placed throughout the nation.
While Atomic Annie never actually experienced combat, the essence of bold experimentation and uncertainty that characterized the early nuclear age is reflected in her legend. She reminds us how rapidly military technology could change—what was on the leading edge a moment ago might become outdated overnight. For historians and military buffs, Atomic Annie provides an intriguing insight into a daring era of Cold War innovation.