The atomic bomb is a powerful, explosive nuclear weapon. It is fueled by the fission of the nuclei of specific amounts of plutonium or uranium, in a chain reaction. The strength of the explosion created by one of these bombs is equal to the strength of an explosion created by thousands of tons of TNT.
The atomic bomb was first created in the early twentieth century. Physicists in the United States and Europe had discovered that the fission of uranium could be used to create a deadly explosive weapon. A letter was sent to U.S. president Franklin D. Roosevelt by Albert Einstein that described this discovery and warned him of its potential dangers if developed by other nations. The Manhattan Project was established by the U.S. government in 1942 so the country could develop an atomic device. A team under the command of United States Army Brigadier General Leslie R. Groves designed and built the first atomic bombs, directed by J. Robert Oppenheimer. This type of bomb was first tested at Alamogordo, New Mexico, on July 16, 1945. The amount of energy that was released by this explosion alone was equivalent to twenty thousand tons of TNT.
Many nations have tested nuclear devices, in the atmosphere, under the earth, and under the oceans. Only the United States of America, Russia, Great Britain, France, and China openly admit to possessing these nuclear weapons. Many other nations, however, are thought to have the capability to assemble these items quickly.
The only times that nuclear weapons were used in a conflict between nations was near the end of World War II, in an attempt to get Japan to surrender to the United States. The first atomic bomb was dropped on the Japanese city of Hiroshima. Over one hundred thousand people were killed by "Little Boy," the bomb that was dropped on this city. After Japan still did not surrender, another bomb was dropped on Nagasaki, another Japanese city. "Fat Man," as this bomb was nicknamed, was estimated to