What happens now after Russia suspends the last nuclear arms treaty with the U.S.?

In 1985, Soviet leader Mikhail Gorbachev and U.S. President Ronald Reagan made a breakthrough when they jointly declared, "a nuclear war cannot be won and must never be fought."

That phrase has lived on, evoked by leaders of both countries. It was affirmed as recently as January 2022, by Russian President Vladimir Putin, President Biden and the leaders of China, France and the U.K., all of which have nuclear weapons and permanent seats on the U.N. Security Council. But the following month, Putin launched a full-scale invasion of Ukraine, and Russia used nuclear threats in an attempt to intimidate other nations from intervening.

Now Putin says Russia "is suspending its participation" in New START, the last remaining nuclear weapons treaty between the U.S. and Russia. The treaty, which took effect in 2011, is set to expire in February 2026.

New START allows each country to verify the weapons pact is being followed, by inspecting the other country's nuclear arsenal multiple times each year. The treaty also requires regular communications about an array of military equipment and operations, to avoid misunderstandings or accidents.

Russia and the U.S. hold the vast majority of the world's nuclear weapons, with each possessing some 4,000 warheads.

Putin made it clear that Russia wasn't abandoning the treaty entirely — and the country clarified on Tuesday that it won't seek to bulk up its nuclear arsenal.

To learn what Putin and Russia hope to gain by this move — and how it affects the broader security picture — we spoke to two experts: Lynn Rusten, vice president of the Global Nuclear Policy Program at the Nuclear Threat Initiative in Washington, D.C.; and Sarah Bidgood, director of the Eurasia Nonproliferation Program at the James Martin Center for Nonproliferation Studies in Monterey, Calif.

Their responses have been lightly edited, for length and clarity.

First things first: Are we heading into a new nuclear arms race?

"I think you could argue that we were already heading in that direction, but it really depends on what Putin means when he says that he is suspending Russia's participation in New START," a treaty with many components, Bidgood said.

"This is not Putin saying, 'I'm going to break out of the treaty's limits and now I'm going to deploy thousands more nuclear weapons,' " Rusten said. "I think it's about a supposedly legal justification for not resuming inspections." [More on that below.]

"No matter what, this development does not bode well for the future of arms control and keeping arms racing in check," Bidgood said.

"We're not in a nuclear arms race today," Rusten said. "But it's very concerning that we soon will be, because the bottom line is, this is the last nuclear treaty governing nuclear weapons of the United States and Russia that is in force. And obviously it's under incredible strain now, and potentially unraveling. It's set to expire in three years, and there's no dialogue going on between the U.S. and Russia about what would come after that."

Didn't the U.S. already accuse Russia of violating the New START treaty?

The treaty includes on-site inspections — but they were halted by mutual agreement over COVID-19 protocols. For months, the U.S. has been trying to resume them. Russia has refused.

"The State Department's 2023 New START annual implementation report found that Russia was not in compliance with the treaty because it would not permit the United States to conduct on-site inspections, and it did not convene a meeting of the Bilateral Consultative Commission, or BCC, within the set timeline," Bidgood said.

Russia says it will continue to inform the U.S. about any ballistic missile launches — but it hasn't said with clarity whether it will continue sending notifications about the movement of a broad range of strategic military assets.

"Every time a strategic item that's subject to the treaty, like a bomber or a submarine, moves, you send a notification," Rusten said. "So those are really important and they've been going on seamlessly throughout," even in the absence of inspections.

"If Russia halts data exchanges and notifications as required by the treaty in addition to on-site inspections and meetings of the BCC, it would make it much more difficult to verify Russia's compliance with the treaty limits," Bidgood said. "It would also eliminate important sources of transparency, predictability, and regular communication between Washington and Moscow, which are arguably more necessary now than ever."

Putin halted Russia's participation in the nuclear treaty one day after President Biden visited Ukraine. Is that a coincidence?

Putin and his government are accusing the U.S. of conducting a hybrid war against Russia and maliciously escalating the Ukraine conflict, alleging that the U.S. has fundamentally altered the security environment.

"I think it's more tied to the fact that the United States, two weeks ago, formally called out Russia as being in violation of the treaty," Rusten said. "The Russians, who actually do tend to be very legalistic in this kind of stuff, are putting forward their legal rationale for why they're justified in not hosting on-site inspections under New START. So I don't think it had to do anything to do with Biden's visit, to be honest."

"A 'suspension' is a term of art [meaning it has a particular legal meaning]," Rusten said. "When one party isn't complying with a treaty, it's one of the options available to the aggrieved party. Now the problem with this is, for arms control treaties, that should only be used if the U.S. were violating New START.

"Russia is linking it more broadly to our support of Ukraine. I don't think the U.S. State Department lawyers would say that's a legitimate use of that sort of right under international law."

Bidgood said, "It indicates to me that the Russian leadership no longer believes that arms control with the United States should be walled off from the bigger ups and downs of bilateral relations as it was during some of the most difficult moments of the Cold War."

"Nuclear arms control was treated as something that needs to go on because it's in the mutual interest," Rusten said. "It's been completely infected now by the broader geopolitical differences between the United States and Russia. So it's troubling."

Has a treaty like this ever survived one party announcing that it's hitting the pause button?

"Not of which I am aware," Bidgood said. "What I think is important to note, though, is that — as Andrey Baklitskiy of [the United Nations Institute for Disarmament Research] points out — suspending participation is a political decision that can be reversed. What we don't know is, under what circumstances would or could that happen?

"I'm not sure this treaty is going to survive to the end of its duration. And I don't see how we're going to have another agreement in place to replace it, if we can't even get to the negotiating table," Rusten said. "It is very concerning that we are hurtling toward a moment where for the first time in probably 70 years, where U.S. and Russian nuclear forces will be completely unconstrained."

What about that famous phrase, that nuclear war cannot be won? Does it carry the same weight as in the past? Or is its power eroding, along with nuclear controls?

"I think its significance really depends on how states behave," Bidgood said. "If you affirm, as Putin has, that a nuclear war cannot be won and must never be fought, but then also engage in nuclear saber-rattling, then it seems to me that these words ring pretty hollow."

"In January of 2022, for the first time, the leaders of the U.S., Russia, China, France and the U.K. made that statement jointly in writing," Rusten said.

"That's really significant," she added. "And that should be a platform on which to build, and step back from this brink that we have walked up to and that Putin's walking up to, and take meaningful steps to make sure that a nuclear war isn't fought, because it can't be won. And it can't even advance Putin's war aims in Ukraine, or globally."

This is the last nuclear weapons treaty between the U.S. and Russia. But what about the broader Nuclear Non-Proliferation Treaty?

"The NPT is an essential part of the nonproliferation and disarmament regime," Bidgood said. "Article VI of that treaty obligates all states' parties — nuclear weapon states and non — to 'pursue negotiations in good faith on effective measures relating to cessation of the nuclear arms race at an early date and to nuclear disarmament, and on a treaty on general and complete disarmament under strict and effective international control.' "

"It creates a mandate to engage in negotiations," Bidgood said, "which is really important in this environment. But what we need are the outcomes of those negotiations."

The NPT, which came into effect in 1970 and has 191 signatory states, also includes inspections. But it lacks the mutual connections New START provides between the world's two biggest nuclear powers.

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