Nuclear risk during the Russian invasion of Ukraine, particularly from the Russian Federation, created a major international crisis within the context of the Second Cold War.
From 24 February to 30 March 2022, Russian forces looted the equipment of the Chernobyl nuclear power plant and obtained radioactive materials. On 27 February 2022, President Vladimir Putin ordered Russia's nuclear forces to go into a state of high alert, and Russia carried out its first test launch of the RS-28 Sarmat ICBM on 20 April 2022. On 24 April, Russian Foreign Minister Sergey Lavrov warned that further support of Ukraine could cause tensions which could potentially lead to World War III, and US Secretary of Defense Lloyd Austin responded by saying that Russia's nuclear war rhetoric was "dangerous and unhelpful."
In the aftermath of the 2022 Kherson counteroffensive, Russia began to think on a potential tactical nuclear strike in Ukraine to turn the tide of the war. On 21 September, Putin announced a partial mobilization of conscripts and warned that Russia would use nuclear weapons to defend Russian territory. Russian statesmen Dmitry Medvedev and Ramzan Kadyrov repeatedly called on the government to use nuclear weapons against Ukraine or the west; while Kadyrov sought the use of low-yield nuclear weapons in response to the loss of Lyman on 1 October, Medvedev called for a nuclear strike on Ukraine if Ukrainians attempted to recapture Russian-annexed Ukrainian territories. In October 2022, Russian defense minister Sergey Shoygu accused Ukraine of planning to use a radioactive dirty bomb on Ukrainian territory, prompting concerns in the West that Russia was preparing to stage a false flag attack.
In January 2023, Speaker of the Duma Vyacheslav Volodin warned that, if Washington and NATO countries continued to supply weapons that would be used to strike Russian cities, Russia would retaliate with more powerful weapons. On 21 February 2023, Putin suspended Russia's participation in New START, the last remaining nuclear weapons treaty with the USA. On 25 March 2023, Putin announced his plans to install Russian tactical nuclear weapons in Belarus.
On 20 September 2024, Russia tested its newest ICBM, the RS-28 Sarmat, only for the missile to fail and destroy the launch silo and its surrounding facilities. On 25 September, Putin warned the West that, if attacked with conventional weapons (such as Storm Shadow and ATACMS missiles), Russia would consider a nuclear retaliation. Two days later, President Alexander Lukashenko - claiming that Ukrainian forces were amassing on the Belarusian border - threatened to use nuclear weapons if attacked by the West.
On 17 November, after Russia launched its largest aerial attack on Ukraine in months, President Joe Biden lifted restrictions on the Ukrainian use of US weapons for attacks deep inside Russia. In response to a Ukrainian ATACMS strike on targets in Bryansk Oblast on 19 November, Putin signed a decree that allowed Russia to use nuclear weapons in response to conventional attacks by a non-nuclear state supported by a nuclear power, reasoning that the Ukrainians must not have been able to carry out the missile strikes on Russia without the help of American instructors. The next day, Russia sowed panic in Kyiv by circulating fake online messages about a massive looming missile and drone attack, leading the USA, Italy, and Greece to temporarily close their Kyiv embassies. On 21 November 2024, Russia warned that the opening of a new US military base at Redzikowo in Poland on 13 November heightened the "overall level of nuclear danger," but Poland responded that there were no nuclear missiles at the base, which was instead meant to intercept short- to intermediate-range ballistic missiles. On 6 December 2024, Russia and Belarus signed an agreement offering security guarantees to Belarus including nuclear security and the possible use of Russian nuclear weapons to repel aggressions.