Nuclear war weapons are explosive devices that employ the physical principles of atomic and nuclear science to unleash massive amounts of force and energy. They are regarded as the most dangerous technology currently on the planet and are considered to be a weapon of mass destruction. The United States is the only country to use nuclear war weapons in a non-testing situation, destroying the Japanese cities of Hiroshima and Nagasaki in 1945.
Fusion or fission bombs typically are the only two types of nuclear war weapons. Fission nuclear weapons are commonly known as atom bombs. They use the science of atomic fission to achieve a supercritical mass, employing fissile materials like plutonium or enriched uranium to set off a chain reaction. Fusion nuclear weapons, known commonly as hydrogen bombs, also use the principles of atomic fission, but because of the higher quantities of energy they generate, this also yields fusion that in turn creates a more violent explosion.
With the advent of nuclear war weapons, world politics adjusted to the dangers and challenges of this new technology. The continued development of these weapons led to arm races between the Soviet Union and the United States called the Cold War. Other countries such as France also sought to develop nuclear weapons for what was viewed as a necessary security measure. The arms race led to more advanced and deadly types of nuclear weapons being produced.
Realizing this dangerous trend in the arms race, attempts to stop the growing number of nuclear weapons included acts such as the nuclear Non-Proliferation Treaty (NPT), which intended to limit their production. Organizations like the International Atomic Energy Agency (IAEA) attempt to monitor against the possible proliferation of nuclear weapons and encourage friendly usage of nuclear technology.
It is estimated that the number of countries in the world with nuclear weapons is approximately 20. As of 2009, only five nations are officially recognized as nuclear weapons states: Russia, China, France, the United Kingdom, and the United States. Countries such as India, Pakistan, and North Korea have all tested nuclear weapons. Israel is suspected to have in excess of 200 nuclear weapons, but has never confirmed or denied this publicly.
The most dangerous nuclear weapon ever produced by man was the Tsar Bomba, a Russian hydrogen bomb that was designed to generate an explosion equivalent to 100 megatons of TNT. Due to the concern about nuclear fallout, only half of a Tsar Bomba was ever made and was tested in 1961. It is the most powerful explosion ever made by humankind.