If you’ve been following the news lately, you’ve probably heard about the U.S. Air Force’s recent use of “bunker buster” bombs in Iran. These aren’t just any bombs—they’re the GBU-57/B Massive Ordnance Penetrators, or MOPs, and they’re designed to do something most weapons can’t: break through mountains of rock and reinforced concrete to reach some of the world’s most heavily protected sites. The bombing of Iran’s nuclear sites at Fordow and Natanz has placed these bombs in the limelight and created significant questions regarding their real role in today’s geopolitics.
So why are bunker busters so special? Unlike traditional bombs that are all brute explosive power, they are precision and penetration. Ryan Brobst, a Foundation for Defense of Democracies munitions expert, explains the trick: their hardened steel body. This allows them to dig deep into the ground before blowing up. The GBU-57/B is enormous—30,000 pounds and 20 feet long—but it contains only a fifth of that as actual explosive material. The rest is constructed to withstand the crushing force of crashing through layers of dirt and concrete. As Brobst puts it, it’s less about creating a huge boom and more about arriving precisely in the right location before exploding.
Even so, as destructive as these bombs are, this past weekend’s bombing of Iran showed their limitations, too. Currently, the only airplane that can deliver the MOP is the B-2 Spirit stealth bomber, and only two at a time. In what’s come to be referred to as Operation Midnight Hammer, the U.S. released 14 MOPs—12 on Fordow and two on Natanz. Subsequent satellite imagery revealed huge craters and severe structural damage. But independent analysts such as Jeffrey Lewis of the Middlebury Institute and David Albright of the Institute for Science and International Security argue that the actual objective—removing the pool of highly enriched uranium in Iran—might not have been met. Activity before the strikes suggested that key materials may have been moved ahead of time, meaning the bombs destroyed infrastructure but likely missed the core of the program.
That brings us to what’s next: building smarter, more capable bunker busters. The Air Force is already developing a Next Generation Penetrator, or NGP, designed to be lighter, more accurate, and effective even in environments where GPS signals are jammed or unavailable. This new weapon might incorporate sophisticated guidance systems, sensors to trigger when the bomb has crossed into a target chamber, and even rocket boosters to allow it to attack from further away. The aim is to have a family of weapons that is flexible enough to deal with a variety of hard-to-reach targets—be it China’s missile silos, Russia’s command bunkers, or North Korea’s underground tunnels.
Why the urgency? Since more and more countries are digging deeper—literally. China, for example, has been building enormous underground complexes, such as a 1,500-acre command center outside Beijing and hundreds of first-strike-resistant missile silos. North Korea and Iran have gone underground as well, with much of their key military infrastructure. Experts such as Hans Kristensen have pointed out that these bunkers are conceived so that a nation’s nuclear capability can survive an attack and still retaliate—a central element of contemporary deterrence policy.
Even the most sophisticated bunker buster has its limits, however. As International Crisis Group’s Ali Vaez reminds us, you can blow up equipment and facilities, but you can’t destroy knowledge. Iran’s nuclear program, for instance, would be rebuilt, particularly if the attack heightens its incentive. Military action may slow things down for a year or two, but it seldom stops such programs altogether. Indeed, as Doreen Horschig of the Center for Strategic and International Studies explains, attacks instead tend to have the opposite effect—strengthening a nation’s will and moving their efforts further underground.
There is also the possibility of unintended consequences. Striking command centers or missile silos in a country such as China may easily be perceived as an effort to take out leadership or disable nuclear capabilities. Such misinterpretation might escalate matters seriously. Specialists such as Brian McLean have cautioned that even conventional strikes against sensitive targets may be misinterpreted as a first strike with devastating effects.
So yes, bunker busters are changing what’s possible in warfare. They provide a means to strike at targets previously regarded as out of reach. But they’re not a panacea. Their application carries grave risks, tactical and political. The true challenge is not to create better bombs but to understand when and how to employ them—matching power with purpose, and acknowledging that some of the world’s most intractable challenges cannot be addressed by military means alone.
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