Vladimir Putin marked the one-year mark of his brutal war of aggression with some nuclear saber-rattling. Speaking to Russian parliament, in a defiant address the day after President Joe Biden made a surprise Ukraine trip to meet with Volodymyr Zelenskyy, the authoritarian announced that his government would be “suspending its participation” in the New START Treaty, the last nonproliferation between Washington and Moscow. It’s unclear what, exactly, that will mean, especially considering Russia has already been defying key provisions of the accord. But it is unquestionably yet another dangerous escalation by Putin, at a point in his Ukraine offensive when nuclear concerns are high. “The announcement by Russia that it’s suspending participation in New START is deeply unfortunate and irresponsible,” Secretary of State Antony Blinken told reporters after Putin’s speech. “We’ll be watching carefully to see what Russia actually does.” 

Putin has been threatening to go nuclear since the beginning of his Ukraine invasion, launching his bombing campaign in February 2022 with a warning that international attempts to interfere with his plans will bring about “consequences greater than any you have faced in history.” He hasn’t made good on that threat, even as the United States and a coalition of western democracies have contributed military aid to Ukraine’s formidable defense. But the risk has continued to  increase, as one expert told me last year. That's particularly true as Putin’s military adventure fails. 

In suspending Russia’s participation in New START, Putin may be making his most reckless move yet; as NATO Secretary-General Jens Stoltenberg put it Tuesday, “the whole arms control architecture has been dismantled.”

“I strongly encourage Russia to reconsider its decision,” Stoltenberg said. 

New START — which was signed by Barack Obama and Dmitry Medvedev in 2010, implemented in 2011, and renewed by Biden and Putin in 2021 — puts limits on the U.S. and Russian nuclear arsenals and intercontinental ballistic missiles, and includes verification measures. Both countries paused those verification measures at the outset of the COVID-19 pandemic, but Russia refused to resume inspections last year, drawing warnings from the U.S. that Russia was threatening the stability of the arms control treaty. Putin on Tuesday said he would not “withdraw” completely from the treaty. But he did seem to close the door on international inspections. “Our relations have degraded,” he told Russian parliament, “and that’s completely and utterly the U.S.’s fault.”

Putin also blamed Ukraine and its western allies for the war he’s been waging in the country: “They were the ones who started the war,” Putin said. “We used force and continue to use it to stop it.”

That’s an obvious lie; as National Security Adviser Jake Sullivan put it to reporters Tuesday, “If Russia stops fighting the war in Ukraine and goes home, the war ends. If Ukraine stops fighting and the United States and the coalition stops helping them fight, Ukraine disappears from the map. So, I think that kind of tells you everything you need to know about who’s responsible for this war.” But if there was one thing clear in Putin’s bluster Tuesday, it was that he has no intention of reversing course. Biden, in his trip to Kyiv Monday and his own speech in Poland on Tuesday, meanwhile, claimed forcefully that Ukraine “stands” and that the U.S.-led coalition will continue its support as long as it takes. “He thought he could outlast us,” Biden said of Putin Monday. “But he was dead wrong.”