Soviet Union and weapons of mass destruction

The Soviet Union had, by 1991, the world's largest stockpiles of nuclear, biological, and chemical weapons. It carried out its first nuclear test in 1949 and its first multi-stage thermonuclear test in 1955. It was one of the five nuclear-weapon states of the Non-Proliferation Treaty, and its biological warfare program was in violation of its ratification of the Biological Weapons Convention. These programs were inherited primarily by Russia.

In 1991, the Soviet Union possessed approximately 29,000 nuclear warheads. The Soviet Armed Forces operated a nuclear triad that deployed over 10,000 strategic nuclear weapons: 6,280 warheads assigned to the Strategic Rocket Forces' 1,334 intercontinental ballistic missiles, 3,626 warheads to the Soviet Navy's 914 submarine-launched ballistic missiles, and 974 cruise missiles and bombs to Long Range Aviation's 106 Tu-95MS and Tu-160 bombers.

The Soviet Union conducted 715 nuclear tests, second only to the United States. These were primarily at Semipalatinsk Test Site, and Novaya Zemlya, where the most powerful nuclear test ever, the Tsar Bomba at 50 megatons, was conducted in 1961. The Soviet Union, with the US and UK, joined the 1963 Partial Nuclear Test Ban Treaty banning non-underground tests. Its nuclear weapons infrastructure saw many radioactive contamination events; the 1957 Kyshtym disaster remains the worst military accident on the International Nuclear and Radiological Event Scale.

The global Cold War saw many nuclear crises. During the 1962 Cuban Missile Crisis, Soviet nuclear warheads and missiles were briefly stationed in Cuba, often considered the closest call with World War III. Nuclear tensions again crescendoed during the 1969 Sino-Soviet border conflict, as Soviet leadership threatened a massive nuclear attack on China. Soviet nuclear weapons were also stationed in the Warsaw Pact countries of Czechoslovakia, East Germany, Hungary, and Poland, as well as Mongolia and potentially Egypt.

Following the December 1991 dissolution of the Union, tactical warheads stationed across post-Soviet states were withdrawn to Russia by May 1992. Strategic warheads between Belarus, Ukraine, and Kazakhstan were also withdrawn by 1996, under the Lisbon Protocol and Budapest Memorandum.

The Soviet chemical weapons program became the largest in world history. Russia in 1993 declared almost 40,000 tons of chemical weapons. The program produced Novichok, VR, sarin, and soman nerve agents, as well as lewisite, mustard, and phosgene, and others. In 1978, Bulgarian dissident Georgi Markov was killed in London, allegedly with the toxin ricin, by Bulgaria's State Security with the aid of the Soviet KGB.

The Soviet biological weapons program was the world's largest, longest, and most sophisticated biological warfare project. It weaponized and stockpiled the biological agents that cause anthrax, plague, tularemia, smallpox, botulism and others. Genetic engineering improved agent stability and antibiotic resistance. The program employed a peak of 65,000 people and annually produced, for example, 100 tons of smallpox. The Sverdlovsk anthrax leak, which led to at least 68 deaths, began to reveal the extent of the program, continued by defectors including Ken Alibek and Vladimir Pasechnik.