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US builds next-generation bunker buster with China in mind
After blasting Iran's nuke bunkers with 13-ton bombs, the US is racing to build a smarter, sleeker penetrator for the next war, possibly with China.
This month, The War Zone (TWZ) reported that in the wake of the US Air Force's first combat use of the 13,000-kilogram GBU-57/B massive ordnance penetrator during the June strikes on Iran's Fordow and Natanz nuclear facilities under Operation Midnight Hammer, the US Department of Defense has accelerated efforts to develop a successor: the next generation penetrator (NGP).
The strikes, which involved 14 MOPs delivered exclusively by B-2 bombers, underscored both the weapon's precision and its operational limitations, particularly in light of the B-21 Raider's reduced payload capacity. A February 2024 US Air Force contracting notice outlines NGP requirements, including sub-9,900-kilogram warheads capable of precision strikes with a circular error probable of within 2.2 meters.
Notably, the NGP may feature standoff capability via propulsion systems, improved void-sensing or embedded fuzing technologies, and enhanced or scalable terminal effects. The push for a successor, spurred by lessons from past MOP development and growing global interest in deeply buried facilities, targets adversaries beyond Iran, including North Korea, China, and Russia.
The US Air Force aims to receive initial prototypes within two years of contract award, though a complete operational deployment timeline remains unspecified, according to the same February 2024 USAF notice. The future NGP is likely to form part of the Long Range Strike system, alongside platforms like the B-21 and the AGM-181A Long-Range Stand-Off (LRSO) missile, making it a critical asset for penetrating hardened targets.
This need to address hardened targets more effectively, highlighted by possible limitations in the Iran strikes, may have prompted the US to fast-track NGP development, especially with peer adversaries like China in mind.
Multiple media outlets cited a leaked US Defense Intelligence Agency (DIA) report stating that US strikes on Iran's nuclear facilities failed to destroy the core of the program and merely set it back by months.
Du Wenlong noted in the South China Morning Post that Iran's Fordow site lies 80 meters underground, 30 meters deeper than the GBU-57's stated penetration capability, raising doubts as to whether the strike hit critical infrastructure.
Song Zhongping said in the same article that although the US dropped 14 bombs, satellite imagery showed six craters, suggesting two bombs may have been aimed at each target, possibly to reinforce penetration. He added that while some infrastructure may have been damaged, complete elimination is implausible.
US Secretary of Defense Pete Hegseth downplayed the DIA report's findings, calling them 'preliminary,' and noting that the report itself states battle damage assessment takes weeks to complete. Hegseth said the report was not coordinated with the intelligence community and suffers from low confidence due to information gaps.
These Iranian lessons could foreshadow far more complex strike dilemmas in a potential conflict with China. In a November 2024 RAND report, Nathan Beauchamp-Mustafaga and others at RAND noted that if initial US strikes on China's maritime and surface assets fail, the US may need to launch long-range conventional attacks against China's buried inland facilities.
Beauchamp-Mustafaga and others wrote that command-and-control nodes and missile storage sites are essential to sustaining People's Liberation Army (PLA) operations.
Satellite imagery cited by Newsweek in May 2025 shows a 1,500-acre site dubbed 'Beijing Military City' near Qinglonghu, southwest of the capital, with deep pits believed to house hardened bunkers capable of sheltering China's leadership in a nuclear war.
Hans Kristensen and others wrote in the Bulletin of the Atomic Scientists in March 2025 that China built over 320 underground missile silos between 2021 and 2025 at Yumen in Gansu, Hami in Xinjiang, and Ordos in Inner Mongolia, significantly expanding its nuclear deterrent capabilities.
They stated these silos, with standardized layouts, are designed for solid-fuel DF-41 ICBMs with potential launch-on-warning capability, supported by hardened command infrastructure and possibly nearby underground storage. They also noted continued DF-5B silo construction, reinforcing survivability through dual platforms.
Furthermore, Greg Weaver argued in an April 2025 Atlantic Council report that standoff capability is essential for enhancing US aircraft survivability when striking mainland China.
He noted that China's advanced air defenses and long-range missiles pose serious threats to forward-deployed US aircraft, making it vital to use standoff delivery systems that launch from outside the range of Chinese defenses.
Yet even with advanced penetrators and standoff options, strikes on the Chinese mainland carry severe risks. In a 2021 Journal of Indo-Pacific Affairs article, Brian McLean argued that while some strategists believe China can differentiate between conventional and nuclear attacks, hitting leadership bunkers or missile forces might be mistaken for a decapitation or disarmament attempt.
He warned that even conventional strikes affecting China's nuclear posture or regime stability could provoke a nuclear response, especially if China perceives its second-strike capability as compromised.
As the US weighs options beyond tactical reach, the broader question of deterrence comes into play. McLean said the best way to avoid escalation may be a strategy of deterrence by denial, convincing China not to attack Taiwan in the first place.
However, Chen Xi wrote in a September 2022 article for the Center for Strategic and International Studies (CSIS) that deterrence by denial hinges on forward-deployed forces and regional basing, both of which are increasingly vulnerable to China's growing missile capabilities and anti-access/area denial systems.
Chen cautioned that this posture could fuel perceptions of encirclement or US intent to strike first, raising escalation risks. He also pointed to practical limitations, including the difficulty of dispersing assets across allied territories, uncertain host-nation support, and ambiguous defense commitments that may weaken US credibility.
