What Is the Bomb Israel Needs from the U.S. to Quickly Destroy Fordow?

As Israel confronts the prospect of a nuclear-armed Islamic Republic of Iran, one question hangs over every war room, every intelligence briefing, and every allied consultation: What if we have to strike Fordow? The Fordow Fuel Enrichment Plant, buried deep beneath the mountains near Qom, is the most fortified nuclear facility Iran possesses, and it is precisely the kind of target for which the United States developed one of the most powerful conventional weapons in military history: the GBU-57A/B Massive Ordnance Penetrator, or MOP.

The GBU-57: An Engineering Marvel

The GBU-57A/B is a 30,000-pound, precision-guided, bunker-busting bomb designed specifically to destroy hardened and deeply buried targets. It is the heaviest non-nuclear weapon in the U.S. Air Force’s inventory and exists to answer a single mission requirement: defeat the kinds of facilities that would otherwise require a nuclear warhead to destroy.

This weapon is not for use against conventional battlefield targets. It is a strategic asset designed to eliminate threats buried hundreds of feet underground, such as command centers, weapons caches, and, most notably, nuclear enrichment facilities protected by both distance and reinforced construction.

Core Specifications

• Weight: ~30,000 pounds (13,600 kg)

• Platform: B-2 Spirit stealth bomber (the only aircraft currently able to deploy the MOP)

This is not a weapon that can be mounted on an F-15 or F-35. It requires the internal bomb bays and high-altitude delivery capabilities of the B-2, which combines both payload capacity and the stealth necessary to penetrate advanced air defense environments.

How It Works: Science of Destruction

The GBU-57 operates on a simple but devastating principle: kinetic energy and delayed blast detonation. When released from high altitude, typically by a B-2 bomber flying above 30,000 feet, the bomb accelerates to near-supersonic speeds under the force of gravity alone. Upon impact, its dense, specially hardened steel casing allows it to bore through layers of soil, granite, and reinforced concrete without breaking apart.

Unlike ordinary bombs that detonate on impact or near the surface, the MOP uses a smart, delay-fuzed explosive trigger. This allows it to explode only after penetrating to the desired depth, releasing an enormous blast pressure from within the target. The effect is akin to setting off an underground earthquake inside a hardened facility, causing walls to buckle, ceilings to collapse, and machinery to be vaporized.

In military terms, the weapon creates a catastrophic loss of function within the target zone. The facility is not just damaged. It is incapacitated.

MOAB vs. MOP: A Key Distinction

The GBU-43/B Massive Ordnance Air Blast, commonly known as the MOAB or the “Mother of All Bombs,” is often confused with the MOP. The MOAB is designed for surface blast effects, not penetration. It weighs around 21,600 pounds and contains over 18,000 pounds of high-explosive slurry, intended to destroy large concentrations of troops, cave complexes, or soft infrastructure. It detonates in the air, generating a massive overpressure wave across a wide area.

The MOAB was used only once in combat, during an April 2017 strike in Afghanistan that targeted an Islamic State tunnel network in Nangarhar province. The explosion reportedly killed nearly 100 fighters and collapsed dozens of entry points. However, it is not a suitable weapon for attacking deep, reinforced targets like Fordow.

Has the GBU-57 Ever Been Used?

To date, the U.S. military has never confirmed operational use of the GBU-57A/B in combat. It is a strategic weapon held in reserve for the highest-value, hardest-to-reach targets, where no other conventional bomb would suffice. It was developed explicitly to give the United States, and potentially its closest allies under exceptional circumstances, a non-nuclear means of targeting deeply buried facilities, especially nuclear infrastructure.

While many of its tests have been documented, actual use has likely been deterred by the diplomatic, strategic, and escalation risks associated with targeting fortified nuclear sites, particularly in adversarial countries like Iran or North Korea.

Why Fordow Is the Ultimate MOP Target

The Fordow facility is not just underground. It is inside a mountain, roughly 260 to 295 feet below the surface. Iran’s engineers designed it to survive even advanced airstrikes. The facility is thought to be constructed beneath at least 80 meters of rock, potentially reinforced by concrete and blast-resistant barriers. It is one of the most protected uranium enrichment plants on Earth.

Fordow’s depth and fortification render it immune to standard air-to-ground munitions. Even advanced Israeli bunker busters like the GBU-28 would likely fail to reach the centrifuge halls.

Some analysts believe that two MOPs may be required to guarantee mission success at Fordow. The first would weaken or breach the protective layers, and the second, following in short succession, could then reach and detonate inside the heart of the facility. This tandem-strike approach would maximize the likelihood of collapsing the internal chambers or destroying centrifuges beyond repair.

Could Fordow Be Attacked Another Way?

While the GBU-57 is the most capable conventional weapon for destroying the Fordow facility, it is not the only potential option. Israel has demonstrated alternative approaches, most notably in Operation Many Ways in 2024, where Israel conducted a complex, multi-domain campaign deep inside Syrian territory. That operation involved deception, intelligence penetration, cyber disruption, precision strikes, and a special forces raid on the ground to eliminate the high-value missile construction facility by placing explosive inside it and then extracting the Israeli soldiers. A similarly bold campaign could theoretically be designed to target Fordow, possibly involving cyber attacks to disable critical systems, electronic warfare, or even special operations forces inserted to destroy key components from within. However, such an approach would carry significantly higher risks, including mission failure, and loss of personnel. Compared to these contingencies, the GBU-57 remains the most direct, reliable, and strategically low-risk option to ensure the physical destruction of Fordow’s deeply buried enrichment infrastructure.

A Strategic Choice for the United States

As Israel weighs its military options against Iran’s rapidly advancing nuclear program, the question is not whether it has the will to strike Fordow. It is whether it has the means. The United States is the only country in the world with the capability to field the GBU-57. Granting Israel access to the weapon would involve not only transferring the munition but also addressing the delivery platform, a logistical and geopolitical decision of the highest order.

There is no substitute for the GBU-57 in this mission set. It is not just the bomb Israel needs. It is the only bomb that can do the job.

John Spencer is executive director of the Urban Warfare Institute. He is the coauthor of Understanding Urban Warfare

Learn more at www.johnspenceronline.com

You can also follow him on 'X' at: @SpencerGuard

Substack: https://substack.com/@spencerguard

The views expressed in this article are the writer's own.