A powerful bunker-buster bomb developed by the United States is the only known non-nuclear weapon that can destroy Iran’s deeply buried nuclear sites. President Donald Trump is believed to favour this weapon if the US decides to assist Israel in striking Iran’s underground nuclear infrastructure.
The weapon in question is the GBU-57, also called the Massive Ordnance Penetrator. This 30,000-pound warhead can dig as deep as 200 feet underground before it detonates. Israel does not possess this bomb, even though it has vowed to stop Iran from building a nuclear bomb.
Over the past week, Israel has struck several Iranian targets. These attacks killed senior commanders and damaged multiple above-ground installations. However, questions remain about how effective the strikes have been against Iran’s most secure nuclear assets.
Behnam Ben Taleblu, who leads the Iran program at the conservative think tank Foundation for Defence of Democracies (FDD), says Iran’s missile sites, launch platforms, bases, and nuclear personnel have all taken major hits. Yet, he admits doubts remain. “There are still serious questions about whether Israel reached the core of Iran’s nuclear programme,” Taleblu said.
One key facility, Fordo, is buried so deep that no Israeli bomb can reach it. The International Atomic Energy Agency (IAEA) confirmed that Fordo, located in the mountains south of Tehran, remains untouched. This makes the site a top target in any future military plan.
“Everyone is watching Fordo,” said Taleblu. “It’s buried under roughly 300 feet of rock and concrete.”
Mark Schwartz, a former US Army lieutenant general now working with the Rand Corporation, stated that only the US has the conventional capacity to destroy Fordo. That capability lies in the GBU-57 bunker-buster bomb.
The GBU-57 is not an ordinary bomb. It is engineered to pierce through thick rock and reinforced concrete before exploding. Unlike typical bombs that explode on or near impact, this one goes deep underground first. According to Masao Dahlgren from the Center for Strategic and International Studies (CSIS), this bomb uses a thick steel casing and a delayed fuse. This prevents it from detonating too early due to extreme pressure and shock.
The design of the bunker-buster bomb began in the early 2000s. Boeing received an order for 20 units in 2009. It is 6.6 meters long and weighs over 13 tonnes. Only one aircraft can carry it — the US Air Force’s B-2 Bomber.
These stealth bombers can carry two GBU-57s each. Satellite images from May showed some B-2s stationed at Diego Garcia, a joint US-UK base in the Indian Ocean. By mid-June, they had left. However, they can reach the Middle East directly from the US, a mission type already performed in the past.
Dahlgren explained that these bombers have flown missions to the Middle East before. Their stealth allows them to bypass radar and carry out high-risk strikes. Schwartz added that Israel’s air superiority over Iran lowers the threat to American bombers during such missions.
Still, one bomb may not be enough. “It won’t be a one-and-done strike,” Schwartz warned. He believes multiple bombs will be needed to destroy facilities as fortified as Fordo.
Using the bunker-buster bomb won’t come without political cost. Taleblu warned that a direct US strike would bring serious diplomatic consequences. He also stressed that military action is not the only route.
Without access to the GBU-57, Israel may resort to alternative methods. These include attacking entry points, cutting power supplies, or collapsing tunnels, as they did at Natanz earlier.
While diplomacy remains an option, the GBU-57 bunker-buster bomb stands as the most effective conventional weapon against Iran’s hardened nuclear sites. Its presence in America’s arsenal keeps it central to any possible military plan targeting Fordo.