"Despite an overall decrease in the number of nuclear warheads in 2019, all nuclear weapon-possessing states continue to modernize their nuclear arsenals." This was the key finding of the SIPRI Yearbook 2020.
According to the Stockholm International Peace Research Institute (SIPRI), the total number of nuclear weapons at the start of 2020 was 13 400, owned by the United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel and the Democratic People’s Republic of Korea (North Korea). This was a decrease of 3.4 percent fromSIPRI's estimates at the beginning of 2019.
The Sweden-based institue related that decrease of 465 nuclear weapons to "the dismantlement of retired nuclear weapons by Russia and the USA—which together still possess over 90 per cent of global nuclear weapons."
"Russia and the USA have extensive and expensive programmes under way to replace and modernise their nuclear warheads, missile and aircraft delivery systems, and nuclear weapon production facilities. Both countries have also given new or expanded roles to nuclear weapons in their military plans and doctrines, which marks a significant reversal of the post-cold war trend towards the gradual marginalisation of nuclear weapons," says SIPRI's press release.
Although Russia and the United States possess the majority of the nuclear weapons, but other nuclear-armed states are either developing or deploying new weapon systems or have announced their intention to do so. The press release adds:
"China is in the middle of a significant modernisation of its nuclear arsenal. It is developing a so-called nuclear triad for the first time, made up of new land- and sea-based missiles and nuclear-capable aircraft. India and Pakistan are slowly increasing the size and diversity of their nuclear forces, while North Korea continues to prioritise its military nuclear programme as a central element of its national security strategy. Although North Korea adhered to its self-declared moratorium on the testing of nuclear weapons and long-range ballistic missiles in 2019, during the year it conducted multiple flight tests of shorter-range ballistic missiles, including several new types of system."