Top U.S. officials aimed to explain why a new Nuclear Posture Review departs from long-held views expressed by President Joe Biden. The Biden administration’s nuclear strategy retains the decades-old policy that the U.S. nuclear arsenal could be used to deter or respond to significant attacks on America or its allies. Biden had previously promoted a shift to a policy in which the “sole purpose” of nuclear weapons would be to deter or respond to nuclear attacks.

“Deterrence has not changed that much over the years,” Richard Johnson, the deputy assistant secretary of defense for nuclear and countering weapons of mass destruction policy, said at an event hosted by the Atlantic Council on Nov. 1. The Biden administration’s Nuclear Posture Review dismissed the Trump administration’s position that nuclear weapons existed to “hedge against an uncertain future” but retained a policy that deems nuclear weapons to be a fundamental part of America’s security strategy.

“But we are at a specific moment now, where I think we do see increases in concerns,” Johnson added, referring to Russia’s renewed invasion of Ukraine and nuclear saber-rattling by President Vladimir Putin as well as the growth of China’s nuclear stockpile.

During his tenure as vice president in the Obama administration and the 2020 campaign, Biden said he wanted to adopt a “sole purpose” doctrine stating that the U.S. would use nuclear weapons only to deter or respond to nuclear attacks.

“The next administration will put forward its own policies,” Biden said in a speech in Jan. 11, 2017, less than two weeks before the end of the Obama-Biden administration. “But, seven years after the Nuclear Posture Review charge, the President and I strongly believe we have made enough progress that deterring—and, if necessary, retaliating against—a nuclear attack should be the sole purpose of the U.S. nuclear arsenal.”

Almost six years later, Biden chose not to adopt that action as President. Instead, the document states that while the “fundamental role” of nuclear weapons is to deter nuclear attacks, the U.S. might use nuclear weapons in “extreme circumstances,” borrowing language from the Obama administration’s 2010 Nuclear Posture Review adopted when Biden was vice president.

“We think that the declaratory policy that we’ve selected is stable and sensible and, frankly, stabilizing,” Johnson said. “But it is true that there are—for a narrow range of high consequence, strategic attacks that would have those sorts of strategic effects using non-nuclear means—that potentially there could be nuclear employment.”

Biden was pressured by U.S. allies in Europe and the Indo-Pacific not to shift to a policy of “sole purpose.” Allies have also opposed adopting a policy of “no first use” meaning the U.S. would never be the first to use nuclear weapons in a conflict. Many countries feared that by stating the U.S. would only use nuclear weapons in a nuclear conflict, Russia and China might be encouraged to launch devastating attacks without resorting to nuclear weapons.

U.S. allies “were very vocal with the White House, and State and Defense Departments, about this issue,” said Jon Wolfsthal, who served as senior director for arms control and nonproliferation at the National Security Council from 2014 to 2017 and is now a senior adviser for Global Zero, a group that is advocating the elimination of nuclear weapons. “They are worried about anything that could be seen as a weakening of America’s commitment to their defense. And given the importance Biden gave to rebuilding alliances, those concerns won out over the substantive debate about whether threatening first use was credible or necessary.”

U.S. officials acknowledged that after consulting with American allies and military officials, the administration decided not to shift to a “sole purpose” doctrine, though it remains a long-term ambition.

“We spent many, many months talking to lots of allies in a process that I somewhat inappropriately called nuclear speed dating, where we talked to many, many allies, both in our Euro-Atlantic region and NATO, and in the Indo-Pacific to get their perspective on this,” Johnson said. “The document also makes very clear that we still have as a goal to move towards a sole purpose declaration, but that we’ll have to identify concrete steps to do that and work with our allies and partners to get there, but because of some of these, sort of a narrow range of these high-consequence attacks, that could have strategic effects using non-nuclear means, especially some that we see, particularly affecting our allies and partners, we felt we couldn’t move in that direction at this time.”

The document intentionally did not lay out what attacks might rise to the level of “strategic.”

“The Nuclear Posture Review does not make a definition or provide examples of what we mean by a narrow range of high-consequence strategic attacks,” Johnson said. “What we do say is that we think that they are a very narrow range, and we think that the bar for nuclear employment in such cases is very high.”

The Biden administration reiterates the view that NATO will remain a nuclear alliance. NATO recently conducted its annual Steadfast Noon nuclear exercise, which practices putting U.S. nuclear weapons on allied fighters.

While the New START treaty limits some of Russia’s long-range nuclear weapons until 2026, China is building an arsenal of around 1,000 nuclear weapons it plans to field by the end of the decade, according to the 2022 Nuclear Posture Review.

“No matter what we do, in 2026 that treaty will expire,” said Alexandra Bell, the State Department’s deputy assistant secretary in the Bureau of Arms Control, Verification, and Compliance. “We don’t understand where China is going with this.”

China and Russia are not engaged in arms control talks with the U.S.

“We’ll be facing a world in which there are potentially no constraints over the two largest nuclear arsenals in the world for the first time in over 50 years,” Bell added. “It’s not a safer world.”

The Nuclear Posture Review originates from the Department of Defense, but the decision to use nuclear weapons is ultimately up to the President. The Nuclear Posture Review, while considering views from the U.S. military and American allies, is a product of Biden’s thinking, the U.S. officials said.

“We forwarded our options to the President, and the President decided, and this is the decision that he made with this particular approach,” Johnson said.