North Korea and weapons of mass destruction

North Korea has a military nuclear weapons program and, as of early 2020, is estimated to have an arsenal of approximately 30 to 40 nuclear weapons and sufficient production of fissile material for six to seven nuclear weapons per year. North Korea has also stockpiled a significant quantity of chemical and biological weapons. In 2003, North Korea withdrew from the Treaty on the Non-Proliferation of Nuclear Weapons (NPT). Since 2006, the country has been conducting a series of six nuclear tests at increasing levels of expertise, prompting the imposition of sanctions. North Korea showed an interest in developing nuclear weapons since the 1950s. The nuclear program can be traced back to about 1962, when North Korea committed itself to what it called "all-fortressization", which was the beginning of the hyper-militarized North Korea of today. In 1963, North Korea asked the Soviet Union for help in developing nuclear weapons, but was refused. The Soviet Union agreed to help North Korea develop a peaceful nuclear energy program, including the training of nuclear scientists. Later, China, after its nuclear tests, similarly rejected North Korean requests for help with developing nuclear weapons. Soviet engineers took part in the construction of the Yongbyon Nuclear Scientific Research Center and began construction of an IRT-2000 research reactor in 1963, which became operational in 1965 and was upgraded to 8 MW in 1974. In 1979, North Korea began to build a second research reactor in Yongbyon, as well as an ore processing plant and a fuel rod fabrication plant. North Korea's nuclear weapons program dates back to the 1980s. Focusing on practical uses of nuclear energy and the completion of a nuclear weapon development system, North Korea began to operate facilities for uranium fabrication and conversion, and conducted high-explosive detonation tests. In 1985 North Korea ratified the NPT but did not include the required safeguards agreement with the IAEA until 1992.