The bomb that devastated Nagasaki on 9 August 1945 was called 'Fat Man'.
Compared to 'Little Boy', the bomb dropped on Hiroshima, the 'Fat Man' was a bigger, more complex design that was plutonium-based.
The codenames 'Fat Man' and 'Little Boy' were inspired by John Huston's 1941 film The Maltese Falcon.
The US's initial hit list, as per History Hit, had five cities: Kokura, Hiroshima, Yokohama, Niigata and Kyoto. However, Kyoto was spared because the then-US Secretary of War, Henry Stimson was fond of the ancient Japanese capital.
Before the devastating bombs, US Air Force dropped pamphlets in Japan. While these didn't specifically warn of an impending nuclear attack on the two cities, they promised "prompt and utter destruction," urging civilians to flee.
The Nagasaki bombing caused the death of some 60,000-80,000 people or around 20% of the population. Meanwhile, an estimated 90,000-166,000 people died in the Hiroshima bombing (6 August 1945).
The Fat Man obliterated around 23% of Nagasaki's buildings and 70% of its industrial zone.