The United States will build a new nuclear gravity bomb.

The US Department of Defense announced on Friday that the government was moving forward with the development of a new version of the B61 nuclear gravity bomb.

The bomb called the B61-13, would have a similar performance to the B61-7 and would replace some of those older gravity bombs, the Pentagon said in its announcement. The performance of the B61-7 is greater than that of the B61-12, the most recent bomb added to the military arsenal.

The Pentagon said the decision to build this weapon was made to reflect the changing security environment in line with the 2022 Nuclear Posture Review. That study said the military needed to modernize its nuclear forces to deter its two main competitors adequately With nuclear weapons, China and Russia.

The B61-13 will use the same modern safety and precision features now built into the B61-12, the Pentagon said in a fact sheet accompanying the statement. It would also give the president more options to attack “tougher, larger-area military targets,” the Pentagon said, as the department works to retire legacy bombs like the B61-7 and B83-1.

Hans Kristensen, a nuclear weapons expert at the Federation of American Scientists who was briefed by the Pentagon on the bomb earlier this week, told Defense News that the weapon would incorporate the same warheads as the B61-7 of the 1980s—in 1990, it was transplanted to a Shell and tail kit of the same style as the B61-12.

Kristensen said the creation of this bomb is likely intended as a commitment to break a years-long disagreement between Democrats and Republicans over the fate of the massive four-decade-old B83-1 bomb.

Former President Barack Obama tried to get rid of the 1.2-megaton B83-1, the last remaining megaton bomb in the country’s nuclear arsenal that would explode with 80 times the force of the bomb dropped on Hiroshima in 1945. But his successor, Former President Donald Trump, reversed that decision.

President Joe Biden has since revived efforts to get rid of B83. But key Republican legislators have objected, saying the B83-1 is needed to hit hard, deeply buried targets.

The maximum yield of the B61-7 – and by extension of the new variant – is 360 kilotons, Kristensen said, while the B61-12 has a maximum yield of 50 kilotons.

“This is a sweetener for the hardliners in Congress, who are basically saying, ‘Okay, guys, you want something with high performance,’” Kristensen said. “There are a small number of them here… but you also get one with a tail kit that will be more accurate.”

House Armed Services Committee Chairman Mike Rogers, R-Alabama, and Sen. Roger Wicker of Mississippi, the ranking Republican on the Senate Armed Services Committee, said in a statement that they welcome the creation of a new B61 variant, but that “it is only a modest step in the right direction.”

“The B61-13 is not a long-term solution, but it will provide our commanders, particularly in [the Pacific and European regions], more flexibility against these sets of targets,” Rogers and Wicker said. “As the Strategic Posture Commission recently noted, China and Russia are in the middle of an arms race, and the United States is advancing in the same place. “A drastic transformation of our deterrence posture, not incremental or gradual changes, is required to address this threat.”

The Pentagon said that the creation of this bomb would not lead to an overall increase in the size of the military arsenal. The United States plans to reduce the amount of B61-12 it will produce by the same amount of B61-13 it builds.

Kristensen said defense officials have indicated that very few B61-13s are expected to be produced, in the order of a few dozen. He doubted that their creation, along with the retirement of the B61-7s, would lead to a major decline, if any, in the number of gravity bombs in the US arsenal, which he said is between 400 and 500.

If it approves and funds B61-13, the Department of Energy’s National Nuclear Security Administration will produce it. The Pentagon claimed in its announcement that modern aircraft could deliver this bomb.

In a follow-up statement, a Pentagon spokesperson said it will include the B-21 Raider stealth bomber that the Air Force is now developing with Northrop Grumman. But the United States now has no plan to deploy it on the F-35 Joint Strike Fighter, the Pentagon said.

But whether the creation of the B61-13 will ultimately be a positive development is “the million-dollar question,” Kristensen said.

“If you work for the administration and you don’t want to spend money maintaining the [B]83, then it’s a good position,” Kristensen said. “If you work outside and watch what’s going on, you might want to say it’s unfortunate that we have to deploy nuclear weapons as a kind of nuclear bargaining in Congress.”

“It’s probably not a new phenomenon,” he added. “But we understand that the administration has decided that this is what it needs to convince defense hawks to get rid of the [B]83.”

Stephen Losey