Tony Sobieski
Background info on the 240mm

Two units utilized the 240mm howitzer in Korea, the 213th and 159th Field Artilleries. The 240mm arrived in Early April 1953 and fired it's first 'official' fire mission on May 1st 1953 (communist May Day) in what at the time was considered a spectacular event. The first round was fired by Baker battery 213th at a target called 'the donut' by aerial observers. While the first round was just supposed to be a ceremonial shot, it struck an ammo dump directly on top of 'the donut' which set off a chain reaction and blew part of the top of the hill off. The aerial observer said 'holy shit' at witnessing the round hit.

The 240mm shell weighed 360 pounds. A total of 5943 rounds were fired between 1 May and 27 July 1953. I believe the piece required over a dozen men to operate, four were required to load a shell. The range was 25,000 yards, and powder increments were used. If you hear of a rumor that the 280mm 'Atomic Annie' gun was in Korea (I've seen this float around the internet) that is actually wrong, it was the 240mm. The 280mm used the same carriage and was originally a re-bored 240mm tube for testing.

There is also a rumor (unsubstantiated but I have read some US military history journals that reference it) that Eisenhower wanted the rumor spread that the UN had nuclear artillery moved to Korea to force the Chinese to the truce table. Now, that may be true, but the real reason was multiple. WWII era 155mm ammunition supply was depleted, combined with a general steel strike in the US, combined with the fact that by mid-late 1952 the war was reverting back into old style 'trench warfare' reminiscent of WWI, the available US artillery (except for the three 8-inch battalions, which were very spread out) just did not have the 'punch' to hit the deep bunkers and fortifications that were by now being built by the Chinese, forced the US military to look for options. It was at this point they saw that there was an ample supply of 240mm shell in stock, so they 'de-mothballed' twelve 240mm howitzers, had a core group of officers trained, and sent them to Korea.