These bombings caused injuries that resulted in the deaths of approximately 200,000 civilians and military personnel. Army Air Forces detonated a plutonium implosion-type fission bomb nicknamed ' Fat Man' over the Japanese city of Nagasaki. Army Air Forces detonated a uranium gun-type fission bomb nicknamed ' Little Boy' over the Japanese city of Hiroshima three days later, on August 9, the U.S. Nuclear weapons have only twice been used in war, both times by the United States against Japan near the end of World War II. 7.1 Effects of nuclear explosions on human health.Nuclear weapons have been deployed twice in war, by the United States against the Japanese cities of Hiroshima and Nagasaki in 1945 during World War II. Since they are weapons of mass destruction, the proliferation of nuclear weapons is a focus of international relations policy. Ī nuclear device no larger than a conventional bomb can devastate an entire city by blast, fire, and radiation. A thermonuclear weapon weighing as little as 600 pounds (270 kg) can release energy equal to more than 1.2 megatonnes of TNT (5.0 PJ). Nuclear bombs have had yields between 10 tons TNT (the W54) and 50 megatons for the Tsar Bomba (see TNT equivalent). The first thermonuclear ('hydrogen') bomb test released energy approximately equal to 10 million tons of TNT (42 PJ). The first test of a fission ('atomic') bomb released an amount of energy approximately equal to 20,000 tons of TNT (84 TJ). Both bomb types release large quantities of energy from relatively small amounts of matter.

A nuclear weapon (also known as an atom bomb, atomic bomb, nuclear bomb or nuclear warhead, and colloquially as an A-bomb or nuke) is an explosive device that derives its destructive force from nuclear reactions, either fission (fission bomb) or a combination of fission and fusion reactions ( thermonuclear bomb), producing a nuclear explosion.

Fission bomb