The United States is the first and only country to use nuclear weapons in the history of the world. These attacks came in August, 1945, during the final stages of World War II against the Empire of Japan. Two cities targeted by the U.S. were Hiroshima and Nagasaki. The war in Europe was over in May of that year, with Nazi Germany's surrender, but the Japanese carried on. The U.S. and its allies conducted a firebombing campaign against the Japanese. It devastated the country, but they would not surrender. The allies were looking at a costly campaign to invade the Japanese mainland. The Japanese were determined to fight to the last person to defend their country, if necessary. This was a major factor in the decision to use the atomic bomb.
The U.S., along with China and the United Kingdom, called for Japan's surrender in July 1945 with a threat of devastation, but Japan refused. On August 9, the first bomb was dropped on the city of Hiroshima. Nicknamed "Little Boy," the bomb killed approximately 90,000 to 170,000 Japanese citizens. The blast completely destroyed the city. Three days later, a second bomb, nicknamed "Fat Man," destroyed the city of Nagasaki. That bomb killed an estimated 60,000 to 80,000 Japanese citizens. About half of the total deaths were immediate. The remainder of the deaths came months after, when the survivors of the initial blast became sick from radiation poisoning, and injuries.
On August 15, after the two atomic bomb attacks, and a declaration of war on Japan by the Soviet Union, Japan decided to surrender. The reasoning behind the decision to use nuclear weapons on Japan is debated to this date. Many say that the bombs saved Japanese, and American lives. The argument is that because of Japanese determination, many more lives would have been lost. In any event, the two attacks are the only nuclear attacks in world history.