Countries with Nuclear Weapons
Russia is supposed to have most nuclear warheads in the world. It has almost 11,000 nuclear warheads out of which 2430 are active. The Soviet Union tested its first nuclear weapon ("Joe-1") in 1949, in a crash project developed partially with espionage obtained during and after World War II. The USSR was the second nation to have developed and tested a nuclear weapon. The direct motivation for their weapons development was to achieve a balance of power during the Cold War. It tested its first megaton-range hydrogen bomb ("RDS-37") in 1955. The Soviet Union also tested the most powerful explosive ever detonated by humans, ("Tsar Bomba"), with a theoretical yield of 100 megatons, intentionally reduced to 50 when detonated.
2. United States
US currently has 1950 active warheads out of 8500 total warheads. It is said that at height of cold war it had almost 32000 warheads. The United States developed the first atomic weapons during World War II in co-operation with the United Kingdom and Canada as part of the Manhattan Project, out of the fear that Nazi Germany would develop them first. It tested the first nuclear weapon in 1945 ("Trinity"), and remains the only country to have used nuclear weapons against another nation, during the atomic bombings of Hiroshima and Nagasaki.
3. United Kingdom
UK has 160 active warheads out of 225 total warheads. The United Kingdom tested its first nuclear weapon ("Hurricane") in 1952, drawing largely on data gained while collaborating with the United States during the Manhattan Project. The United Kingdom was the third country in the world after the USA and USSR to develop and test a nuclear weapon. Its program was motivated to have an independent deterrent against the USSR, while also maintaining its status as a great power. It tested its first hydrogen bomb in 1957, making it the third country to do so after the USA and USSR.
France has 290 active warheads out of 300 total warheads. France tested its first nuclear weapon in 1960, based mostly on its own research. It was motivated by the Suez Crisis diplomatic tension vis-à-vis both the USSR and the Free World allies United States and United Kingdom. It was also relevant to retain great power status, alongside the United Kingdom, during the post-colonial Cold War. France tested its first hydrogen bomb in 1968 ("Opération Canopus"). After the Cold War, France has disarmed 175 warheads with the reduction and modernization of its arsenal that has now evolved to a dual system based on submarine-launched ballistic missiles (SLBMs) and medium-range air-to-surface missiles. However new nuclear weapons are in development and reformed nuclear squadrons were trained during Enduring Freedom operations in Afghanistan.
China has 240 warheads in total and 180 are supposed to be active ones. China tested its first nuclear weapon device ("596") in 1964 at the Lop Nur test site. The weapon was developed as a deterrent against both the United States and the Soviet Union. China would manage to develop a fission bomb capable of being put onto a nuclear missile only two years after its first detonation. It tested its first hydrogen bomb in 1967, a mere 32 months after testing its first nuclear weapon (the shortest fission-to-fusion development known in history). The country is currently thought to have had a stockpile of around 240 warheads, though because of the limited information available, estimates range from 100 to 400. China is the only NPT nuclear-weapon state to give an unqualified negative security assurance due to its "no first use" policy.
India is not a Party to the Nuclear Non-Proliferation Treaty. India tested what it called a "peaceful nuclear explosive" in 1974 (which became known as "Smiling Buddha"). The test was the first test developed after the creation of the NPT, and created new questions about how civilian nuclear technology could be diverted secretly to weapons purposes (dual-use technology). India’s secret development caused great concern and anger particularly from nations, such as Canada, that had supplied it nuclear reactors for peaceful and power generating needs. It appears to have been primarily motivated as a general deterrent, as well as an attempt to project India as a regional power. India later tested weaponized nuclear warheads in 1998 ("Operation Shakti"), including a thermonuclear device. In July 2005, U.S. President George W. Bush and Indian Prime Minister Manmohan Singh announced plans to conclude an Indo-US civilian nuclear agreement.
Pakistan also is not a Party to the Nuclear Non-Proliferation Treaty. Pakistan covertly developed nuclear weapons over many decades, beginning in the late 1970s. Pakistan first delved into nuclear power after the establishment of its first nuclear power plant near Karachi with equipment and materials supplied mainly by western nations in the early 1970s. Pakistani Prime Minister Zulfiqar Ali Bhutto promised in 1965 that if India can build nuclear weapons then Pakistan would too, "even if we have to eat grass." The United States continued to certify that Pakistan did not possess nuclear weapons until 1990, when sanctions were imposed under the Pressler Amendment, requiring a cutoff of U.S. economic and military assistance to Pakistan. In 1998, Pakistan conducted its first six nuclear tests at the Chagai Hills, in response to the five tests conducted by India a few weeks before. Over the years, Pakistan has developed into a crucial nuclear power.
8. North Korea
North Korea was a Party to the Nuclear Non-Proliferation Treaty, but announced a withdrawal on January 10, 2003, after the United States accused it of having a secret uranium enrichment program and cut off energy assistance under the 1994 Agreed Framework. In February 2005 the North Koreans claimed to possess functional nuclear weapons, though their lack of a test at the time led many experts to doubt the claim. However, in October 2006, North Korea stated that due to growing intimidation by the USA, it would conduct a nuclear test to confirm its nuclear status. North Korea reported a successful nuclear test on October 9, 2006. Most U.S. intelligence officials believe that North Korea did, in fact, test a nuclear device due to radioactive isotopes detected by U.S. aircraft; however, most agree that the test was probably only partially successful. The yield may have been less than a kiloton, which is much smaller than the first successful tests of other powers.