“We've seen agitation between this administration and many of our allies, and there is renewed interest, I think, in many countries, particularly in Europe, Japan, and South Korea, in having their own nuclear-deterrence systems quickly,” Sen. Jack Reed, D-R.I., said at Tuesday’s hearing of the Senate Armed Services Committee. 

Reed asked others at the hearing whether they agreed.

“I don't think you can understate the risk of proliferation,” replied Timothy Morrison, a former deputy assistant to the president for National Security Affairs and senior fellow at the Hudson Institute.

At least some U.S. allies are considering developing nuclear weapons of their own, said Rose Gottemoeller, a former NATO deputy secretary general. 

“I am very concerned about the potential for proliferation, so-called friendly proliferation. I do not think it will be helpful to stability and security,” Gottemoeller said. “There are many, I would say, debates and discussions that have surprised us among our NATO allies. Thursday will see the lapse of the 14-year-old New START agreement, which caps U.S. and Russian deployed strategic nuclear forces at 1,550 warheads and 700 delivery systems. 

Gottemoeller urged the White House to renew the treaty for one year. Other witnesses, including Charles Richard, who as a Navy admiral led U.S. Strategic Command, did not, as it would constrain U.S. weapons development without necessarily stopping Russian violations.

All witnesses agreed the treaty had its limitations. It did not address nuclear-development trends, such as Russia’s development of unmanned submarines  hypersonic missiles, and new tactical or lower-yield weapons that Russia has threatened to use against Ukraine. It also does not involve China, which has expressed skepticism about joining any such talks. 

The collapse of New START was not unexpected, in part due to its limitations. “I think the New START Treaty will go out with a whimper,” said Morrison. 

Less expected was the rise of tensions between the United States and Europe, including President Trump’s threats to seize territory belonging to NATO allies.

On Jan. 25, Swedish Prime Minister Ulf Kristersson confirmed that the country had begun preliminary talks with France and the U.K., Europe’s two nuclear powers, about  potential collaboration on nuclear weapons. This follows remarks last March from Poland’s Prime Minister Donald Tusk that Poland must begin to explore its own options for developing nuclear weapons.

Such developments would have been unthinkable a few years ago, under the U.S. commitment to the “nuclear umbrella”, a guarantee that the United States would use its nuclear weapons in retaliation to any Russian nuclear attack on a NATO nation. But according to one Swedish newspaper, “the umbrella is gone.”

That may be premature. The United States has made no formal announcement that it is pulling back on its guarantee of nuclear protection in Europe. But as Gottemoeller pointed out, the White House has done little to reassure allies.

“The Secretary of War has stated that the United States will continue to extend the nuclear deterrent to our allies. But the fact that we are not seeing the administration really articulate this policy at a high level—neither the National Security Strategy nor the National Defense Strategy addresses it—is leading allies to think about extending nuclear deterrence themselves,” she said.

Sen. Angus King, I-Maine, pointed out during the hearing that “extended deterrence” appeared only once in the new National Security Strategy, which focuses much more on critiquing the European Union.

The witnesses also shared concerns about China’s rapid nuclear-weapons development. By 2035, Pentagon officials have predicted, China will have up to 1,500 warheads to deploy on ICBMs, submarines, and bombers. 

“I think we have never seen a buildup that is proceeding as comprehensively and at this speed,” said Morrison. “I think maybe it breaks some of our models.”

In response, South Korea and other Asian nations are returned to long-abandoned discussions about building their own nukes. 

“Our Asia-Pacific allies are certainly re-examining their own defense needs to include the possibility of them acquiring their own nuclear weapons,” said Richard. “I don't know of any proliferation that is actually occurring. We certainly have a longstanding history and have had successful extended deterrence commitments to both of those, and there are still options available to us.”

None of the witnesses said that the development of a new “Golden Dome” missile shield offered perfect protection against a widening number of nuclear threats. But Richard was adamant that an advanced missile shield, including space-based interceptors, would still make an attack on the United States less likely by “introducing a lack of confidence on the part of your opponent that their attack is going to be successful, yet they will carry all the consequences of having started it.”

Sen. Mark Kelly, D-Ariz., countered that he did not feel that was sufficient. “I am very concerned that we could throw a trillion dollars at a problem that ultimately we will find is unsolvable,” he said. “I really worry about the future for our kids and our grandkids, living in a world where we have multiple countries with potentially thousands and thousands of nuclear weapons.”