These are the bunker buster bombs used by US to hit Iran's nuclear sites

Built to pierce hundreds of feet of rock, the US-only GBU-57 bunker buster bomb may be the world's only weapon capable of reaching Iran's Fordow nuclear site and Israel doesn't have it

President Donald Trump said American bombers struck Iran’s three main nuclear sites on Sunday, pulling the US directly into the Israel-Iran conflict despite his earlier pledges to avoid new wars. Trump said a “payload of bombs” was dropped on Fordow, a uranium-enrichment facility buried deep under a mountain and considered vulnerable only to specialised “bunker buster” munitions. Natanz and Isfahan, two other key nuclear sites, were also targeted. We decode what bunker buster bombs are, how they function, and why they were used in the latest US strikes.

 

Fordow nuclear facility is a highly fortified site carved into a mountainside near Qom, southwest of Tehran. Operational since 2009, the site is believed to be buried 80 metres deep beneath rock and reinforced layers, with an air defence shield backed by Iranian and Russian surface-to-air missile systems.

 

 

 

Fordow’s design makes it nearly impenetrable to conventional military attacks, and it plays a critical role in Iran’s uranium enrichment programme. The International Atomic Energy Agency (IAEA) has confirmed that highly enriched uranium is being produced at the site, raising alarm in Western capitals. The facility is seen as central to Iran’s potential nuclear weapons capability.  But while Israel has struck other targets, like the Natanz centrifuge hall, it lacks the deep-penetration firepower required to destroy Fordow. That capability currently lies exclusively with the United States, in the form of the GBU-57A/B Massive Ordnance Penetrator (MOP).

 

What is a bunker buster bomb and why is it used for hitting Fordow nuclear site?

 

“Bunker buster” is a general term for bombs designed to pierce through soil, rock, or concrete to reach underground bunkers or tunnel networks before detonating. The idea is to neutralise fortified enemy infrastructure buried far below the surface—targets that ordinary bombs can’t reach.

 

The GBU-57A/B is the most advanced bunker buster bomb in the world today. Also called the Massive Ordnance Penetrator (MOP), it was developed specifically to deal with hardened targets like Fordow. 

Why the GBU-57 bunker buster is crucial for deep underground strikes

 

Weighing approximately 30,000 pounds (13,600 kg), it is one of the heaviest precision-guided bombs in existence. It has a length of around 20.5 feet and can burrow through up to 200 feet (61 metres) of soil, rock, or reinforced concrete before exploding.

 

The bomb delivers 10 times more explosive force than its predecessor, the BLU-109. It is made from high-performance steel alloys and retains structural integrity even at high-speed impacts, allowing it to drill deep into targets. The MOP is GPS-guided, enabling high-accuracy strikes on pinpointed coordinates—crucial when targeting bunkers hidden beneath mountains. 

How the US delivers the GBU-57 bunker bomb using B-2 stealth bombers

 

The only operational aircraft configured to deliver the GBU-57A/B is the US Air Force’s B-2 Spirit stealth bomber. The B-2 can carry up to 40,000 pounds, but it has been successfully tested with two MOPs onboard, carrying a total of 60,000 pounds (27,200 kg). Capable of flying 7,000 miles without refuelling and 11,500 miles with aerial refuelling, the B-2 can reach targets anywhere in the world. Its low radar signature allows it to evade air defence systems, giving it access to heavily guarded targets like Fordow. 

How bunker buster bombs like the GBU-57 shape nuclear strike strategies

 

The GBU-57 isn’t just a bomb—it’s a strategic asset. It’s designed for deep strike scenarios involving Iran, North Korea, China, or Russia, where adversaries have fortified key infrastructure underground.

 

As of 2015, at least 20 MOPs had been delivered by Boeing, the prime contractor since 2009. While the exact size of the stockpile is unknown, it is believed to be limited. This adds to the weapon’s scarcity and strategic weight. 

Why Israel wants the GBU-57 to destroy Iran’s Fordow nuclear site

 

With Israel signalling its intent to neutralise Iran’s nuclear programme, and with Fordow considered a non-negotiable target, the question is not just military but political.

 

US President Trump, when asked recently at the G7 summit whether the US would use military force, declined to elaborate. But only the US has the tools to destroy Fordow, and the decision to use the MOP could pull Washington into a broader conflict in West Asia.

 

Israeli officials have stated clearly that the elimination of Fordow is essential. But without the GBU-57 and the B-2 bombers to carry it, Israel cannot strike the facility independently. 

What are the environmental and nuclear fallout risks of striking Fordow?

 

Although the MOP is a conventional (non-nuclear) weapon, targeting a site like Fordow, which houses nuclear material, raises concerns about radioactive contamination. However, past Israeli strikes on the Natanz site caused contamination limited to the facility, according to the IAEA.

 

Nevertheless, the GBU-57A/B Massive Ordnance Penetrator is more than a bomb—it is a weapon of last resort for hardened underground targets. Its use carries enormous strategic, political, and environmental implications. And in the case of Fordow, it may be the only weapon capable of neutralising the threat.