With the changing deterrence dynamics and technological advancements, the United States’ nuclear strategy has long moved away from Cold War mentalities. The focus of nuclear weapon development has shifted from ensuring mass destruction of adversaries to targeting core and high-value targets that have moved into underground bunkers. There is a possibility of introducing successors to the B61-11 specifically designed to destroy deep bunkers. The U.S. military may soon unveil more new variants of the B61 nuclear bomb.
On January 7, the U.S. National Nuclear Security Administration (NNSA) announced the completion of the 17-year, $9 billion B61-12 nuclear bomb upgrade and production, transitioning to the production of the more powerful B61-13.
NNSA Director Jill Hruby stated in the announcement that the agency is providing capabilities at the speed and scale required by the Department of Defense partners and deterrence needs.
Technically, the B61-12 is not a new nuclear weapon; it integrates older models like B61-3, B61-4, B61-7, and B61-10 while updating technologies, consolidating old warheads into new bomb bodies. The recently completed B61-12 differs from previous versions mainly by the addition of a tail kit, including an Inertial Navigation System (INS) kit. Furthermore, other enhancements have been made to the B61-12, details of which largely remain classified. These 12-foot-long, 825-pound bombs are priced significantly higher than their equivalent weight in gold.
Following the completion of the B61-12 Life Extension Program (LEP) production, NNSA will now shift its focus to producing the B61-13 nuclear bomb. The B61-13, announced in October 2023, is capable of yielding a 360-kiloton explosive yield.
While the B61-13 leverages the design of the B61-12, it will be upgraded beyond those designs. The plan for the B61-13 aims to enhance the bomb’s precision, presumably causing more complex effects on targets. Detonating the nuclear bomb closer to the target will increase the likelihood of destroying the target. The power of a single B61-13 theoretically equals that of two B61-12 bombs, capable of demolishing even sturdier facilities.
An even more intriguing development is the potential launch of more new versions of the B61 nuclear bomb series by the U.S. military, possibly including successors to the highly specialized B61-11 variant designed for penetrating deep underground targets.
The U.S. Air Force Nuclear Weapons Center (AFNWC) mentioned in a recent contract notification its explicit intent to develop a potential variant distinct from the B61-12 and B61-13. The notification explains that AFNWC is seeking to expand the support services for B61 nuclear gravity bombs by considering modifications to incorporate tail kit assemblies (TKAs) for the B61-12, B61-13, and any future variants.
AFNWC stated that the B61-13 and future variants will require highly specialized engineering and logistical services to ensure sustained safety and reliability and to maintain the maintainability of the B61-13 and future variants.
Though the U.S. Air Force’s contract notification does not specify which variants of the B61-series they may be interested in, it underscores long-standing issues with the B61-11 and the true successor plans for the B61-11.
The B61-11, deployed in 1997, differs significantly from other models primarily in its reinforced casing, possibly equipped with a depleted uranium penetrator warhead and a rocket booster in the tail, making it specifically designed for penetrating robust underground facilities. It appears that there are not many targets suitable for this type of nuclear bomb, hence the limited quantity of such bombs in U.S. military stockpiles, estimated to be only approximately several dozen.
With the greatly enhanced accuracy of the upgraded B61-12, there have been suggestions to consider replacing the B61-11 and the more powerful megaton-class B83-1 with the B61-12. The higher precision of the new bomb allows for better concentration of destructive power on buried targets, addressing the shortcomings in destructive power of low-yield bombs or the lack of specialized penetration capability.
After 2018, the U.S. government seemingly abandoned this position. In the 2023 U.S. military announcement of the B61-13 plan, it is expected to have a maximum yield equivalent to the existing B61-7, far exceeding that of the B61-12. It will offer additional options for the U.S. President to target specific objectives. U.S. officials stated that the B61-13 program suggests that the U.S. does not rule out the deployment of new types of nuclear penetrating bombs to replace the B61-11 in the future.
In November 2020, Russian President Putin discussed issues relating to Russia’s nuclear command and control infrastructure, revealing a new enhanced strategic command center. It is understood that a specific potential target fitting this description is the Kosvinsky Kamen bunker in Russia, a key driver behind the U.S. development of the B61-11.
Located approximately 300 meters beneath solid granite, the facility is part of Russia’s nuclear command and control functions, doubling as a “government continuity” site to protect core leadership from nuclear strikes or other major emergencies. This system has long been termed a “Doomsday machine,” capable of automatically launching intercontinental ballistic missiles in retaliation in the event of a nuclear attack.
Russia also has a larger comprehensive bunker near Mezhgorye known as the Yamantau Mountain base, about 1,000 meters under quartzite, with limited public knowledge about its facilities, accessible only to authorized personnel.
As the main competitor of the U.S. military, China has been expanding its underground facilities, including constructing large-scale nuclear facilities and new intercontinental ballistic missile launch silos in recent years.
Both North Korea and Iran are increasingly turning to buried facilities, often to counter potential conventional strikes by U.S. forces and other nations.
The U.S. military states that the planned B61-13 aims to provide additional capabilities to target underground hardened targets and larger surface objectives. However, it is estimated that it still may fall short of the unique capabilities of the B61-11. Additionally, it remains unclear how similar tail guidance kits like those of the B61-12 and -13 will integrate with the boost rockets in the tail of the B61-11. Ultimately, achieving precise guidance with the B61-11 could pose a significantly different threat to adversary core leadership.
The U.S. military may also be interested in pursuing other potential variants of the B61 series to gain varying functionalities, including bombs with lower explosive yields. The U.S. Navy has already deployed the Trident II submarine-launched ballistic missile equipped with dedicated low-yield W76-2 nuclear warheads, providing valuable additional flexibility in any future escalation of nuclear conflict.
A non-classified report on the current U.S. nuclear strategy released by the Pentagon in November last year states that the new “Guidance requires all plans for responding to limited nuclear attacks or high-consequence non-nuclear attacks to include related concepts favorable to managing escalation, including reducing the likelihood of a large-scale nuclear attack on the United States and its allies and partners.” As the operational environment becomes increasingly complex, managing upgrades involving nuclear weapons becomes more crucial. This could lead to escalating conflicts becoming more complex and unpredictable to control.
In November last year, the Pentagon Defense Science Board (DSB) also announced the commencement of a new study on “Joint Force Nuclear Survivability.” Threats of using nuclear weapons by Russia surrounding the Ukraine conflict, as well as the nuclear developments of China, North Korea, and Iran, are all key driving factors prompting the U.S. to alter its nuclear strategic posture.
A publicly available memo from the Defense Science Board stated that if adversaries employ nuclear weapons, particularly targeting U.S. allies, or if the U.S. becomes embroiled in a conventional conflict that escalates to nuclear use, endangering military personnel, the U.S. military may be called upon to respond and take action to defeat the adversary.
In essence, the U.S. Air Force contract notification implies a new development direction, focusing on developing a specialized successor for the B61-11. It aims to ensure the elimination of adversary core leadership and other high-value targets, regardless of their concealment in deep, fortified bunkers. While still a nuclear strike option, it has a more targeted approach, delivering more deterrence to a small fraction of key personalities compared to the “wholesale indiscriminate destruction of adversaries in a large-scale nuclear strike.”