Atomic Annie was the first nuclear capable cannon. It was essentially a 240 mm artillery cannon bored out to 280 mm to accomodate the smallest possible shell that could be produced by the US Atomic Energy Commission. The warhead was about 15 kiloton and could be launched about 20 miles.

The gun was first conceived in 1949 and made it to the field by 1953. The barrel was 42 feet long and the entire cannon weighed in at about 75 tons. It was esentially a standard railroad cannon chassis with a solid base, utilizing a dual recoil mechanism for more frequent launching. The base consisted of a swivel mechanism that allowed the gun to be raised and rotated 360 degrees.

The gun itself had no means of propulsion and was transported using two utility trucks that lifted up the gun and carried it. The two trucks operated independently of each other and could move at a top speed of about 35 miles per hour. It took about 8 minutes from stopping the trucks to launch.

Atomic Annie was only fired once, on May 25, 1953 in the atomic test zone in Nevada (I've been told footage of this is contained in the movie Trinity: The Atomic Bomb Movie). While it was deployed in Europe, it was never actually used in battle. Part of the problem was that it was fairly time-consuming to get the gun into appropriate range, due to its relatively slow movement and limited range capability (there was not much adjustment in range, the gun had to be a good 15-20 miles from the target). Because of this, the Russians and Germans were very well aware of the gun and always kept track of its location, easily keeping out of its way.