In an operation that marks a pivotal moment in modern aerial warfare, the United States Air Force (USAF) executed its first combat deployment of the formidable GBU-57 Massive Ordnance Penetrator (MOP) on June 22, 2025. Codenamed Operation Midnight Hammer, the mission saw the release of 14 GBU-57 MOPs against two critical Iranian nuclear sites — Fordo and Natanz. Designed to annihilate deeply buried and hardened targets, these 30,000-pound munitions represent the cutting edge of American bunker-busting capability.
This unprecedented action underscores a decisive shift in Washington’s approach to counterproliferation operations and signals a clear deterrent to adversaries contemplating nuclear ambitions beneath tons of reinforced concrete and rock. However, even as the dust settles over central Iran, a newer, more sophisticated successor to the MOP is already under development: the Next Generation Penetrator (NGP).
Iran’s nuclear program has long relied on buried infrastructure to evade detection and destruction. The Fordo facility, buried under 80 meters of mountain near Qom, and the Natanz complex, another deeply fortified site, have consistently challenged the limits of conventional strike capabilities.
But on June 22, those limits were redefined.
Each GBU-57 MOP, built to penetrate 200 feet (60 meters) of reinforced concrete or rocky terrain before detonation, was precisely directed at command bunkers, uranium enrichment labs, and critical utility nodes.
While official assessments of the strikes are ongoing, satellite imagery and early intelligence reports suggest extensive damage. Underground chambers reportedly collapsed, and secondary detonations — likely caused by damaged storage — were detected.
This was the first time these bombs were used in combat since their development in the early 2010s, and the largest deployment of heavy ordnance in a single USAF operation since the Gulf War.
Weighing in at 30,000 pounds (13,600 kg), the GBU-57A/B is the largest non-nuclear bomb in the American arsenal. Originally developed by Boeing and the Air Force Research Laboratory, it is specifically designed to defeat Hard and Deeply Buried Targets (HDBTs).
- Warhead Class: BLU-127, with 2,100–2,600 kg of high explosive.
- Guidance: Dual-mode GPS and Inertial Navigation System (INS).
- Fuze Technology: Adaptive fuzes capable of detecting structural voids and optimizing detonation timing.
- Delivery Aircraft: Exclusively compatible with the B-2 Spirit stealth bomber, each carrying up to two MOPs.
But despite their destructive power, these munitions lack propulsion, meaning they must be released at high altitude and close to the target. This limits their flexibility in contested environments.
Even before the first GBU-57 entered operational use, the USAF had already turned its sights on what comes next.
In February 2024, a formal contracting notice signaled the start of the Next Generation Penetrator (NGP) program, laying out ambitious requirements that significantly exceed the MOP’s capabilities.
Core Requirements for the NGP:
- Weight: 22,000 pounds or less (lighter than the MOP for expanded platform compatibility).
- Terminal Accuracy: Circular Error Probable (CEP) within 2.2 meters, even in GPS-denied environments.
- Standoff Capabilities: Provision for rocket booster integration, allowing launches from safer distances.
- Fuzing Systems: Embedded adaptive fuzes for variable penetration and blast effects.
- Platform Integration: Compatibility with the B-21 Raider, the USAF’s next-gen stealth bomber.
This vision leverages insights from the 2012 Hard Target Munitions (HTM) Analysis of Alternatives (AoA) and a 2019 AoA Excursion, highlighting the Air Force’s long-term focus on HDBT defeat strategies.
The B-21 Raider, developed by Northrop Grumman, is intended as the stealthy successor to the B-2 Spirit. Smaller, cheaper, and designed for high survivability in contested environments, the B-21 will be a core component of the USAF’s global strike capability.
Crucially, the B-21 is expected to be equipped not just with legacy MOPs but also with the future NGPs. Given its internal weapons bay configuration, the NGP’s reduced weight and enhanced stand-off capabilities are critical for maintaining stealth profiles during missions.
However, due to its smaller frame, each B-21 will likely carry only one MOP, whereas the B-2 can carry two. This limitation, illustrated by the recent operation, implies a higher fleet utilization requirement for future bunker-busting missions.
While the GBU-57 and NGP are designed for heavy bombers, the USAF is also pursuing a parallel line of development: a Global Precision Attack Weapon (GPAW) tailored for stealth fighter platforms like the F-35.
In 2020, reports surfaced detailing the USAF’s interest in a compact, precision-guided bunker buster small enough to fit inside the internal bay of the F-35 Joint Strike Fighter — maintaining stealth integrity while expanding tactical flexibility.
Though still conceptual, the GPAW would fill the niche for tactical-level strikes against medium-depth bunkers, providing commanders with faster response options in theater.
In parallel, the GBU-72/B/B, a 5,000-pound-class guided bunker buster, has already entered limited service. It was reportedly used during a 2024 strike against Houthi targets in Yemen, signaling USAF’s intent to diversify bunker-busting tools beyond the GBU-57.
The demand for enhanced bunker-busting capabilities stems from a global trend: the proliferation of deeply buried military and nuclear infrastructure.
- Russia operates vast underground command posts in the Urals and Moscow region.
- China has constructed entire subterranean cities for military operations, including missile silos and aircraft storage.
- North Korea’s nuclear facilities, like those at Yongbyon, are notoriously hardened and hidden.
- Iran, as demonstrated, has engineered nuclear sites under mountains and concrete.
- The logic is simple: bury it deep enough, and it’s safe from conventional attack.
- But with the advent of MOP and soon the NGP, the USAF aims to invalidate the safety of depth.
These developments are not merely technical—they are strategic. The ability to eliminate HDBTs in a single, precise strike redefines deterrence, alters enemy calculations, and gives policymakers new tools short of nuclear war.
The decision to strike Iranian nuclear sites with bunker buster bombs was likely not taken lightly. It signals a new willingness by the U.S. to enforce red lines — not just with rhetoric or sanctions, but with unprecedented kinetic force.
The operation itself required meticulous planning:
- Stealth ingress routes for B-2 Spirits.
- Electronic warfare to suppress Iranian radar.
- Mid-air refueling coordination for long-range operations.
- Timing and sequencing to maximize bomb penetration and effect.
Experts believe this mission will serve as a test case for refining the performance parameters of the NGP. Data gathered from MOP strikes — blast radius, penetration success, post-strike seismic activity, structural collapse metrics — will feed directly into NGP prototyping.
The future battlefield will not only stretch across deserts and skies but plunge beneath the earth. As adversaries seek shelter in the subterranean realm, the USAF’s evolving bunker buster portfolio aims to deny them refuge.
- The GBU-57 MOP has proven the concept.
- The NGP will scale it for precision, survivability, and reach.
- The GPAW will democratize bunker-busting across platforms.
- The B-21 Raider will deliver it all, silently and unseen.
