Nagasakibomb The mushroom cloud from the Nagasaki bombing on August 9, 1945. Wikipedia

On the morning of August 6, 1945, a lone B-29 bomber dropped a single atomic bomb on the city of Hiroshima in Japan. Soldiers had nicknamed the weapon "Little Boy."

It's estimated that 70,000 people died from the initial blast of the uranium bomb, and that the five-year death toll likely climbed over 200,000, due to the lasting health effects of the massive dose of radiation that survivors received.

Three days later, another aircraft detonated a second bomb over the city of Nagasaki. This one was called "Fat Man," since it used plutonium and would result in an explosion 40% larger than Little Boy's.

That bomb killed an estimated 40,000 in the initial blast and around 140,000 over the next five years. The lower death toll was because people had evacuated the city, including many schoolchildren.

These two atomic bombs — the only ever used in battle — caused considerable damage, but they weren't the biggest bombs the US ever made. The World War II bombings launched the nuclear arms race, as the US and Russia began building bigger and bigger bombs.


The hydrogen bomb nicknamed Castle Bravo, detonated in 1954, had the highest energy of any the US ever tested.

It exploded with the power of 15,000,000 tons of TNT.

By comparison, the Little Boy was equivalent to 18,600 tons of TNT.


The nuclear weapons in the US stockpile these days — which still number around 7,200 — are generally smaller, typically in the 100,000-ton range.



Each pink block represents a ton of TNT, and 1,000 pink blocks represents a kiloton, which is shown as a red block:

nuclear bomb power

A previous version of this post was published by Ashley Lutz.