The US military set off its largest nuclear explosion in testing 69 years ago, but scientists had no idea the blast would be that big

• Dozens of nuclear tests were carried out by the US in the Pacific between 1946 and 1958.
• The largest of these was the detonation of the Castle Bravo device on March 1, 1954. 
• It was 1,000 times more powerful than the atomic bomb that leveled Hiroshima during World War II. 

The US military tested dozens of nuclear weapons in the Pacific in the years following World War II, but none of the blasts compared in size to that of the Castle Bravo test — what a nuclear weapons historian once called "the greatest single radiological disaster in American history."