What countries have nuclear weapons? In the world today, nine countries currently possess nuclear weapons, including the five major countries that occupy the five permanent slots on the United Nations Security Council.
Any discussion about which countries possess nuclear weapons should start by outlining what nuclear weapons are. At its most basic, a nuclear weapon is the most powerful form of explosive known to man. A single modern nuke carries the power of 100,000 (or more) tons of TNT and could kill more than half a million people if detonated in a densely populated area.
Historically speaking, there are three basic types of nuclear weapon:
Historically, fission weapons were referred to as atomic/atom bombs and fusion weapons were called hydrogen bombs. Today, "atomic bomb" has been replaced by "nuclear weapon," which is also used as a general blanket term referring to any of these weapons, and "hydrogen bomb" has been replaced by "thermonuclear weapon."
Nuclear weapons have been used during wartime on only two occasions, both by the United States toward the end of World War II. The first nuclear weapon used during war was a "uranium gun" fission bomb, codenamed "Little Boy", dropped from a Boeing B-29 Superfortress onto the city of Hiroshima, Japan, on August 6, 1945. The bomb exploded with a force estimated to be equivalent to 15,000 tons of TNT, killing an estimated 66,000-80,000 people (long-term effects such as radiation poisoning and bombing-induced leukemia would eventually raise this estimate to 90,000-140,000), injuring 69,000 more, and leveling 4.7 square miles of the city. Yet, despite the bomb's unprecedented destructive power—as well as a renewed declaration of war from the Soviet Union—the Japanese government vowed to fight on. This led the U.S. to plan a follow-up attack on a second target.
On August 9, 1945, a mere three days after the nuclear weapon hit Hiroshima, U.S. bombers detonated a second nuclear weapon, this time a plutonium-core, implosion-type bomb codenamed "Fat Man", just above Nagasaki, Japan. Although clouds and smoke made aiming difficult and caused the bomb to detonate nearly two miles from its intended target, the blast nonetheless killed an estimated 35,000-40,000 people immediately (and roughly 60,000 injured), with long-term effects raising the death toll to 39,000-80,000 lives over time. Faced with the threat of continued bombings, Japan chose to surrender, ending World War II.
The use of nuclear weapons to end World War II sparked an arms race between the nations of the world, particularly the United States and the newly formed Union of Soviet Socialist Republics (U.S.S.R.), in which each country sought to manufacture and prepare as many nuclear weapons as possible. This nuclear proliferation reached its peak of approximately 70,000 missile-mounted nuclear warheads in 1986, then began to decline sharply with mutual disarmament agreements such as Intermediate-Range Nuclear Forces Treaty (INF) of 1987 and the Strategic Arms Reduction Talks that began in the '80s and continued off and on into the early '10s. As of 2021, there are estimated to be just over 13,000 available nuclear warheads in the world.
Eight different nations around the world have successfully detonated nuclear weapons, and a ninth appears to have the capability to do so. The 1970 Treaty on the Non-Proliferation of Nuclear Weapons, otherwise known as the NPT, authorizes the five permanent members of the United Nations Security Council—the United States, Russia, China, France, and the United Kingdom—to possess nuclear weapons on their territory with no need for justification or explanation.
Three additional states have conducted nuclear testing even though they did not sign the NPT: North Korea, India, and Pakistan. Of these three, North Korea's nuclear capability is most notable because the country appears to be violating United Nations resolutions that prohibit North Korea from developing nukes or ballistic missiles. The Middle Eastern country of Israel, known as the Holy Land to many Christians, Muslims, and Jews, is not known to have ever tested nuclear weapons but is known to possess them just the same. Israel’s government refuses to confirm or deny the country's nuclear capabilities.
While any country that uses nuclear power plants to generate electricity could theoretically also develop nuclear weapons, the Comprehensive Nuclear Test Ban Treaty of 1996 proposed that no additional countries be allowed to create or possess nuclear weapons. This includes countries that have never had nukes as well as nations that previously possessed nuclear weapons but for whatever reason no longer do. These countries include South Africa, Belarus, Ukraine, and Kazakhstan.
As of 2021, the United States has an estimated 5,550 nuclear weapons. It is believed that 1,800 are in strategic deployment and another 3750 are in storage or in various states of readiness, but could be made available quickly if the need arose. This is a fraction of what the US had at its peak of 31,225 in 1967 and 22,217 in 1989. Russia has downsized its nuclear arsenal over the years as well, but still possesses roughly 6255 warheads, 1625 of which are strategically deployed and ready to fire.
Russia has the largest arsenal, with 6,255 nuclear warheads.