The success of the June 22 attack as part of Operation Midnight Hammer on the Iranian bunkers where material for nuclear weapons was allegedly stored has emboldened the U.S. Department of Defense (DoD) to further improve its capacity to buster bunkers by developing stronger variants.
And, while this success seems to have encouraged countries like India, Israel, and Turkey to acquire and strengthen similar capacities of their own, China is working on how to counter bunker busters by revealing an alleged flaw with their design.
As their names suggest, bunker busters are weapons designed to destroy heavily protected facilities deep underground, beyond the reach of normal bombs.
The U.S. arsenal has 30,000-pound GBU-57/B Massive Ordnance Penetrator (MOP) bunker buster bombs. Made by Boeing, these are weapons highly capable of penetrating deep underground sites, particularly when used in multiples at nearly the same time.
Apparently, the U.S. delivered 14 MOPs by its B-2 bombers on Iran’s underground nuclear enrichment facilities in Natanz and Fordow. Those penetrated 200 feet of earth and beyond, or more than 25 feet of steel-reinforced concrete.
It may be noted that while not the manufacturer of the bomb itself, Northrop Grumman was contracted to refit the B-2 Spirit bomber to carry the GBU-57, enabling its deployment.
The 20-and-a-half-foot-long GBU-57/B is a precision-guided bomb that consists of a penetrating “warhead,” which has its own designation (BLU-127/B), along with a GPS-assisted inertial navigation system (INS) guidance package, specialized fuzes, and other components.
The explosive content of the MOP, which also has a diameter of 31-and-a-half inches, is only roughly 20 percent of its total weight. The casing is a special ultra-strong alloy known as Eglin Steel (named after an Air Force base in Florida where it was developed).
Apparently, the MOP is dropped from high altitude to smash through rock using sheer kinetic energy. It is fitted with a delay fuse (FMU-143) so that it explodes after penetration rather than on impact.
It is said that there has also been a good bit of research into smart fuzes that, using a microprocessor and an accelerometer, can actually detect what is happening during penetration and explode at precisely the right time to cause the most damage. These fuses are known as hard target smart fuses (HTSF).
It may be noted that the GBU-57/B was first tested in 2007, and its design has been upgraded several times since. It was developed by America’s air force when it found that its existing bunker-busters could not damage Iraqi bunkers during the invasion in 2003.
Incidentally, the MOPs were used for the first time on June 22.
The point to note here is that though the U.S. is not the only country with bunker-busting weaponry, its MOPs are the heaviest in the world, and the size of the MOP means it requires very specialised platforms to carry and drop it. And the B-2 bomber is the only aircraft capable of carrying the massive MOPs – each bomber can hold a pair of the bombs.
And this is the possible reason why the U.S. Air Force wants the new bunker buster that is currently being developed under the name of “Next Generation Penetrator,” or NGP. This new weapon is expected to carry a warhead of less than 22,000 pounds and offer greater accuracy, even in GPS-degraded or denied environments.
The most recent publicly stated requirements for the NGP come from a contracting notice the Air Force put out in February 2024. It called for a warhead weighing 22,000 pounds or less, and that would be “capable of blast/frag [mentation] / and penetration effects,” but did not specify a desired gross weight for the entire munition. No prospective dimensions were provided, either.
“The prototype penetrator warhead design effort should allow integration of technologies acquired and lessons learned under previous penetrator warhead developments to meet performance requirements for the HDBT target set,” the contracting notice added.
“The USAF will consider novel, demonstrated, or fielded Guidance, Navigation & Control (GNC) technologies with viability for integration into a warhead guidance system design that can achieve repeatable, high accuracy performance in GPS-aided, degraded, and/or denied environments.”
The notice also said that a “terminal accuracy” of “CE90 w/in 2.2m both in GPS aided, degraded, and denied environments” was desired. What “CE90 w/in 2.2m” means in layman’s terms is a munition that can hit within 7.2 feet (2.2 meters) of a specified impact point at least 90 percent of the time. This is a very high degree of required accuracy, especially for employment in GPS-degraded or denied environments.
Reportedly, the U.S. is working additionally to ensure that the MOP and any future NGP are not limited by the absence of pre-strike intelligence about the exact depth and/or physical layout, resulting in their inability to penetrate very deeply. Here, specialized fuzing needs are said to be imperative.
Accordingly, work on advanced void-sensing fuzes that can detect when a munition has breached into a sufficiently large space, such as a room in an underground facility, is an area of development that has already been of particular interest for the U.S. military for years now. A fuze that is able to just effectively ‘count’ floors to help determine depth to detonate the bomb at a certain level for maximum damage would also be a useful addition, it is said.
Going by the size of the bunker buster and the platform to deliver it in a nation’s arsenal, the United States seems to be way ahead of others.
Other Nations Keen On Bunker Busters
Though its close ally Israel also operates American-made bunker busters, including the GBU-28 and BLU-109, which are typically dropped from fighter jets such as the F-15, these weapons have a much shallower penetration range and are not capable of reaching extreme depths of fortified sites like Iran’s Fordow nuclear facility.
However, in 2024, Israel reportedly used successive BLU-109 bombs to kill Hezbollah leader Hassan Nasrallah in his underground headquarters in Beirut.
Turkey, America’s NATO ally but often recalcitrant, has just unveiled a new domestically developed penetrating bomb capable of destroying hardened underground targets at the 17th International Defense Industry Fair (IDEF 2025) in Istanbul.
Developed by the Research and Development Center of the Turkish Ministry of Defense, the new munition has been named “NEB HAYALET” (Ghost in Turkish). The weapon is designed to neutralize deeply fortified structures such as command centers, bunkers, and critical infrastructure.
The approximately 2,000-pound (1 ton) class bomb demonstrated strong performance in official tests, reportedly penetrating over 7 meters of high-strength C50 reinforced concrete — roughly five times stronger than that used in standard residential construction — before continuing through an additional 1.5 tons of standard concrete. C50 concrete, with compressive strength exceeding 50 megapascals (MPa), is typically used in military-grade fortified installations.
Unlike the American MOP that requires deployment from specialized strategic bombers, the Turkish NEB HAYALET is based on the standard MK-84 bomb casing. This design ensures compatibility with widely used NATO aircraft, including the Turkish Air Force’s F-16 fighter jets, enhancing deployment flexibility and operational readiness.
Reportedly, development of the NEB HAYALET spanned more than a decade, involving research, prototyping, and qualification in accordance with NATO standards. The munition has completed its certification process and is now slated for operational deployment by the Turkish Armed Forces.
India is reportedly developing its own bunker buster to strike deep underground targets. The 7,500-kg Agni-V-based bunker buster that is under development by India’s Defence Research and Development Organisation (DRDO) is said to be an advanced version of the Agni-V ballistic missile platform.
Unlike the nuclear-tipped Agni-V that has a range of over 5,000 km, this missile is intended to target enemy installations buried beneath layers of concrete, with the ability to penetrate 80 to 100 metres underground.
Apparently, when operationalised, the improvised Agni V would be among the most powerful conventional missiles in the world, it is said.
What About China?
The country has been in the news recently, not because it has developed its own buster, but by claiming to have discovered the vulnerabilities in the likes of the famed GBU-57.
In a study published in China’s Journal of Gun Launch and Control, researchers led by Cui Xingyi from the country’s Northwest Institute of Mechanical and Electrical Engineering have apparently found a potential weakness in the GBU-57.
The study noted that while the MOP’s nose is heavily reinforced, its steel sides are just a few centimeters thick, making the weapon vulnerable to anti-aircraft shells.
Chinese researchers explain that while the GBU-57’s egg-shaped nose deflects direct frontal hits, its sides betray a vulnerable area which could be shattered by a couple of anti-aircraft projectiles.
They say that for a shell to penetrate, it must strike at an angle under 68 degrees; otherwise, it will simply glance off. Their tests also showed that penetration fails beyond 4,900 feet, but within 3,900 feet, heat and shrapnel can ignite the bomb’s inert explosives.
However, many strategic experts are not impressed with the Chinese theory. For them, while the sniper-style interception tactics sound promising in theory, the realities of combat are far harsher. Air forces can launch mass raids to destroy anti-aircraft interceptors before bomber missions begin, eliminating any potential defense.
Secondly, they say that smart bombs often perform final manoeuvres just before impact, making their flight path unpredictable and limiting the opportunity to target within the narrow 3,900-foot effective range, which only lasts for a split second.
Besides, these experts further add, China’s defense systems may not be effective in other regions due to differences in terrain, threat environments, and available technologies.
Thus, it can be said, in sum, that while other countries have developed or are developing bunker-busting capabilities, the U.S. possesses the most advanced and powerful bunker busters currently in operation.
- Author and veteran journalist Prakash Nanda is Chairman of the Editorial Board of the EurAsian Times and has been commenting on politics, foreign policy, and strategic affairs for nearly three decades. He is a former National Fellow of the Indian Council for Historical Research and a recipient of the Seoul Peace Prize Scholarship.
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