Designed to destroy bunkers but dogged by doubts, the US B61-13 nuclear gravity bomb enters a strategic storm of China’s silo surge, fragile US basing and rising allied skepticism over deterrence in Asia.
This month, The War Zone reported that the US has completed its first production unit of the B61-13, a more powerful nuclear bomb variant designed to replace the B61-7 ahead of schedule, according to the Department of Energy (DOE).
The B61-13, based on the B61-12, features advanced safety and guidance systems and a higher yield of 340-360 kilotons, making it effective against hardened underground targets. Production was expedited using streamlined engineering and existing B61 design data.
The Pantex Plant in Texas completed the first unit almost a year ahead of schedule, underscoring the urgency of modernizing the US nuclear deterrent amid increasing global threats.
DOE Secretary Chris Wright emphasized the bomb’s role in enhancing US strategic capabilities under the Trump Administration’s “peace through strength” doctrine. Unlike the B61-12, which is available to NATO allies, the B61-13 is reserved exclusively for US bombers like the B-2 and B-21. This aligns with rising concerns over China and Russia’s growing underground military infrastructure, prompting increased deterrence investments.
While the B61-13 improves targeting capabilities, it does not replace the deeply penetrating B61-11 variant, leaving specific hardened threats beyond immediate reach.
The B61-13’s rollout underscores a sharpened US response to China’s expanding and hardening missile silo network. However, its strategic impact may be undercut by the bomb’s delivery limitations, fragile regional basing posture and growing allied skepticism toward extended deterrence without visible forward deployments.
However, even as China hardens its intercontinental ballistic missile (ICBM) infrastructure, the key question remains: Can US delivery systems like the B61-13 actually threaten them under real-world conditions?
Hans Kristensen and others note in a March 2025 article for the Bulletin of Atomic Scientists that China’s missile silos at Yumen, Hami and Yulin mark a significant expansion of its nuclear arsenal, featuring around 320 ICBM silos built in remote areas out of reach of US cruise missiles.
Kristensen and others add that the silos—likely for DF-31A ICBMs—are laid out in a triangular grid and linked to underground control centers by buried cables. They point out that satellite imagery reveals that each field has numerous support facilities and security infrastructure, suggesting improved survivability and a shift towards a launch-on-warning posture.
As to the hardened features of China’s silo fields, Ryan Snyder mentions in a December 2024 article in the peer-reviewed Science & Global Security journal that these silos are assessed to have structural features comparable to Russian designs, with diameters around 6 meters, suggesting hardened protection for large ICBMs like the DF-5.
Snyder says that while exact values remain classified, available evidence suggests their peak hardness ranges from 1,500 pounds per square inch (PSI), which is on par with Russia’s most fortified silos, to as low as 450 PSI for potential legacy sites. He says these incorporate standard hardening techniques, including shock isolation systems and rattlespace buffers to protect missiles from destructive ground motion.
Highlighting the capability of the B-21 to hit such targets, Mark Gunzinger mentions in a March 2023 Mitchell Institute for Aerospace Studies report that the bomber is designed to penetrate deep into China’s mainland to strike high-value targets critical to nuclear deterrence and conventional warfighting.
Gunzinger says such targets include mobile ballistic missile launchers, command centers, anti-satellite weapon sites and deeply buried facilities beyond the reach of current US standoff munitions.
He emphasizes that the bomber’s stealth, range and payload enable it to operate within China’s dense air defense network, ensuring the US can credibly threaten targets across China’s vast interior. He argues this capability is vital to deterring nuclear coercion and escalation by presenting China with the risk that its strategic assets could be destroyed in a crisis or conflict.
However, Greg Weaver points out in an April 2025 Atlantic Council report that gravity bombs such as the B61-13 must be released in close proximity to the target, with that lack of standoff capability reducing the survivability of the launch aircraft.
In terms of nuclear forward basing, Josh Chang mentions in a January 2025 Real Clear Defense article that the US nuclear posture in the Indo-Pacific is practically non-existent, with its current nuclear theater portfolio in the region built around dual-capable fighter aircraft (DCA) and bombers based in the US mainland, which is insufficient to deter current threats.
Chang notes that the air leg of the US nuclear triad has not been on continuous alert for three decades, minimizing its preparedness for a potential nuclear crisis. He adds that adversary air defense systems and long transit times from the US mainland to the Indo-Pacific strain the situation.
But even if the US considers forward-deploying B-21 bombers in the Indo-Pacific, Thomas Shugart III and Timothy Walton mention in a January 2025 Hudson Institute report that People’s Liberation Army (PLA) missiles, often equipped with submunitions, could neutralize major US air bases like Iwakuni, Diego Garcia or even Langley with as few as 10 missiles.
Shugart and Walton point out that China has invested heavily in hardening over 3,000 aircraft shelters, while the US has largely neglected such defenses, leaving ramp-stationed aircraft, fuel depots and maintenance systems exposed.
They note this vulnerability invites Chinese preemptive strikes and undermines US power projection, unless hardened shelters and resilient infrastructure are urgently fielded. These vulnerabilities suggest that even deploying advanced bombers won’t matter unless US bases can survive a Chinese first strike.
Without upgraded forward basing options, US nuclear upgrades would be largely moot in terms of assuring extended deterrence, argues Peter Lee and Kang Chungku in a February 2024 Asan Institute article.
Citing the case of South Korea, Lee and Kang say that despite enhanced US commitments under the 2023 Washington Declaration, South Korean public confidence in US extended nuclear deterrence has declined, reflecting a broader skepticism among US Indo-Pacific allies.
According to them, this skepticism stems from the absence of concrete measures such as the forward deployment of tactical nuclear weapons, assets still stationed in Europe but long withdrawn from Asia.
Further, Zuzanna Gwadera mentions in a March 2025 article for the International Institute for Strategic Studies (IISS) that the reliability of US extended deterrence in the Indo-Pacific is increasingly questioned as allies like Japan and South Korea weigh the likely effectiveness of the US nuclear umbrella amid shifting geopolitical dynamics.
Ultimately, extended deterrence is as much about perception and posture as it is about hardware. Gwadera raises concerns over the Trump administration’s transactional security approach, as he urges allies to boost defense spending while questioning unconditional US support.
She states that despite reaffirming nuclear guarantees with Japan and South Korea, doubts linger amid China and North Korea’s growing nuclear capabilities. She warns that the erosion of trust in US deterrence could push Japan and South Korea toward indigenous nuclear programs, undermining global non-proliferation efforts.
