Congress appears ready to support Trump’s low-yield nuclear weapons

WASHINGTON — The new low-yield nuclear warheads that President Donald Trump wants to add to the American arsenal look poised to receive backing from Congress, despite an outcry from anti-nuclear advocates and attempts by Democratic lawmakers to defund or limit their introduction.

The addition of the warheads to ballistic-missile submarines has become the most controversial element of the Trump administration’s new nuclear weapons strategy. Critics say the smaller impact of such “battlefield nuclear weapons” makes them more tempting to use in a crisis — therefore lowering the threshold of nuclear war.

But the Trump administration, led by Defense Secretary Jim Mattis, rejects that argument and says the U.S. military must place the low-yield warheads on submarines to ensure that Russia realizes it cannot get away with a limited nuclear attack on a U.S. partner or ally.

In his most detailed justification of the new low-yield W76-2 warhead, Mattis said in a letter to Senate Majority Leader Mitch McConnell, R-Ky., that Russia had increased the number and diversity of its nuclear weapons and issued veiled nuclear threats to U.S. allies.

Without naming Russia, Mattis added that “potential adversaries have openly discussed the benefits of limited nuclear employment.”

“The President’s request for the W76-2, a supplemental capability, is in response to developments in Russian nuclear doctrine, exercises, and its new nuclear capabilities,” Mattis wrote in the June 3 letter obtained by the Washington Post. He called the warhead a “modest adjustment” to the arsenal.

Mattis said the W76-2 “does not require developing a new nuclear warhead or nuclear testing, it does not violate any nuclear arms control treaty, and it does not increase the size of the nuclear stockpile.”

The administration plans to modify an existing high-yield warhead, dating to the 1970s, to achieve the low-yield weapon for use on submarines. Congress has backed those plans.

But critics say that even a modification of an existing warhead would needlessly expand U.S. nuclear capabilities at a time when they should be scaled back.

The House and Senate versions of the annual defense policy bill authorize $65 million to convert some of the highyield W76-1 nuclear warheads deployed on Ohio-class submarines into the smaller-yield variants known as W76-2 warheads. The House has passed its version of the bill that approves the lowyield variants, which the Pentagon hopes to deploy on Trident D5 ballistic missiles by 2020.

The administration has requested an additional $23 million in the coming year’s budget to flight-test the lower-yield warhead variant on a Trident submarine before deployment. The tests would use a dummy warhead without any fissile material.

Though official U.S. nuclear-warhead yields remain classified, experts estimate the new W76-2 would explode with a yield of about 6.5 kilotons, whereas the full-size W76 explodes with a yield of roughly 100 kilotons. By comparison, the warheads the U.S. military dropped on Hiroshima and Nagasaki, Japan, in 1945 exploded with about 15 and 20 kilotons of force, respectively.

The Pentagon’s rationale for putting low-yield warheads on submarines rests on the belief that Russian nuclear doctrine has evolved to include the possibility of a battlefield nuclear attack. U.S. defense officials sometimes call the suspected Russian strategy “escalate to de-escalate.”

The idea is that Russia — which retains a vast arsenal of small and nimble nuclear arms — could employ one against an American ally or partner in a “limited attack.” That would force the United States to choose between responding with a highyield strategic nuclear warhead, all but guaranteeing full-scale nuclear war, or returning fire with a conventional weapon, risking embarrassment or defeat.

The Trump administration believes the W76-2 would convince Russia that any such attempt would result in a reciprocal low-yield nuclear attack.

Mattis sent his two-page document to McConnell in response to a May 22 letter that Democratic California Gov. Jerry Brown and prominent former U.S. officials wrote to the Senate majority leader the previous month decrying the W76-2 as a gateway to nuclear catastrophe.

The letter said the introduction of the warheads was based on a “mistaken and dangerous belief ” that it would be possible to prevent a limited nuclear exchange between Russia and the United States from escalating into an uncontrollable nuclear war.

“Ultimately, the greatest concern about the proposed low-yield Trident warhead is that the president might feel less restrained about using it in a crisis,” the letter said. “When it comes to using a nuclear weapon, restraint is a good thing.”

Mattis, in his rebuttal, rejected the argument out of hand.