At dawn on June 22, 2025, American B-2 Spirit stealth bombers launched the first real combat use of the massive GBU-57 bunker-buster bomb against Iran’s Fordo nuclear facility, buried deep inside a limestone mountain.
Despite its enormous 13-ton weight, the weapon failed to produce the total destruction Washington initially claimed. Early assessments from the Defense Intelligence Agency (DIA) revealed that the attack did not eliminate Iran’s underground program but merely delayed it by several months.
Conflicting statements expose the uncertainty inside the U.S. security establishment
President Donald Trump and Secretary of War Pete Hegseth publicly insisted that Fordo had been “completely destroyed.”
But the intelligence report told a different story.
Days later, the Trump administration informed the UN Security Council that the strike had merely “weakened” Iran’s nuclear capabilities — a noticeably more cautious tone that signaled deep internal doubts about whether the bombs had truly reached the facility’s core.
Fordo survived… and revived the debate over America’s next-generation bomb
Images of deep craters at Fordo and Natanz spread across the media within hours. Soon after, reports resurfaced about the U.S. project to develop a successor to the GBU-57: the Next Generation Penetrator (NGP).
The timing appeared far from coincidental. It suggested an implicit admission that the GBU-57, despite its brute force, had not delivered the decisive performance the Pentagon expected against a heavily fortified mountain complex.
Six consecutive strikes to hit a single point
Military reports revealed that reaching one critical point inside Fordo required six consecutive strikes on the same coordinates.
The first bombs removed the upper layers of rock and concrete, while subsequent bombs continued drilling downward until reaching the deep target area.
This scenario highlighted the extreme difficulty of penetrating facilities buried 70 to 80 meters underground — and the urgent need for a lighter, more efficient, deeper-penetrating weapon.
From brute force to smart power
The Fordo strike exposed the limits of the GBU-57 at the exact moment Washington began accelerating the NGP program.
The new bomb is expected to weigh no more than 10 tons, making it compatible with the next-generation B-21 Raider stealth bomber.
The Pentagon is also considering equipping it with a rocket motor to increase velocity, deepen penetration, and allow launches from far longer distances, reducing exposure to modern air defenses.
Precision guidance: the real battle inside the mountain
Bunker-buster bombs rely on a dual guidance system combining INS and GPS to maintain a precise trajectory toward a narrow tunnel entrance or thick underground ceiling.
Even minor deviations can cause the bomb to explode too early, rendering the mission a failure.
A key feature is the intelligent fuze, which delays detonation by fractions of a second so the bomb can reach sufficient depth before exploding and releasing a seismic shockwave capable of fracturing underground structures from within.
A global underground arms race
The U.S. motivation for a new penetrator weapon goes far beyond Iran.
America’s main adversaries have spent decades turning geological depth into a strategic shield.
North Korea operates an entire underground state of tunnels and missile bases.
China has built the “Great Underground Wall,” a vast network protecting its nuclear forces.
Russia maintains immense underground command facilities in the Ural Mountains.
This global reliance on subterranean defenses forces Washington to rethink deterrence in an era where depth itself is becoming a weapon.
Toward a new, invisible arms race beneath the earth
A stronger U.S. penetrator bomb will inevitably push adversaries to bury their critical infrastructure deeper than before.
This could mark the beginning of a new underground arms race —
a contest between weapons designed to reach deeper,
and infrastructures designed to sink even further into the earth.
A silent race, with no clear endpoint.
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