“It’s cheaper and easier for someone to dig deeper than it is to penetrate through that depth,” noted physicist Raymond Jeanloz, whose research on earth-penetrating weapons has influenced military doctrine over decades. That wisdom never seemed more timely than in the wake of Operation Midnight Hammer, when the world’s best bunker-buster bombs met the underground aspirations of Iran’s nuclear drive.
In June 2025, the United States launched its weaponry at three of Iran’s most vulnerable nuclear facilities: Fordow, Natanz, and Isfahan. The Pentagon’s initial view, supported by President Trump who described the attacks as “a spectacular military success” was that Iran’s enrichment capacity had been “completely and totally obliterated”. However, as reports came through, a more complex picture developed: Fordow alone was seriously disabled, Natanz and Isfahan damaged but still, in the descriptions of several officials, “months” away from possible recovery.
The technical task was daunting. The Fordow plant, buried under 80 to 90 meters of rock, was long thought to be a proving ground for the GBU-57 Massive Ordnance Penetrator a 30,000-pound weapon meant to penetrate through hardened layers before exploding. B-2 Spirit stealth bombers dropped at least a dozen MOPs during the attack, aiming not just at the central enrichment halls but also ventilation shafts, in hopes of maximizing shockwave transmission. Still, as Jeanloz’s estimates and follow-up DIA analysis indicate, penetration depth of the GBU-57 is very sensitive to geology up to 80 meters in silty clay but just 7.9 meters in medium-strength rock. Fordow’s placement under a mountain ridge probably optimized its shielding.
At Natanz, the engineering problem was even more formidable. Iran had been digging new tunnels deeper than Fordow’s, and satellite pictures have uncovered a facility that may be more deeply buried than any other. The United States has bombed Natanz with MOPs, but the officials have confirmed that some of the underground halls were “below where the GBU-57 could reach” (NBC News). Isfahan, on the other hand, was attacked only with Tomahawk cruise missiles, whose subsonic warheads are intended for surface and shallow buried targets not labyrinthine underground tunnels thought to contain much of Iran’s enriched uranium inventory.
The design of Iran’s underground facilities has developed directly in response to Western weaponry. Fordow has five tunnel corridors leading into its main halls, with the enrichment rooms behind hundreds of feet of rock and strengthened concrete. The new Natanz complex, based on open-source analysis, includes even deeper burial and a probable capacity for greater floor space, with several portals and probable helical ramps targeting and destruction by conventional means increasingly daunting.
U.S. Central Command had actually come up with a more ambitious “all-in” plan: a weeks-long operation repeatedly targeting six locations, including additional Iran’s air defense and missile capabilities. But President Trump shunned this plan, reluctant to a long war and heavy casualties for both sides. “We were willing to go all the way in our options, but the president did not want to,” an NBC News source said.
The aftermath is an exercise in the bounds of military technology and hardened engineering. Fordow’s enrichment capability has been delayed by as much as two years, but Natanz and Isfahan can be months away from returning to operations if Iran decides. Intelligence reports indicate that much of Iran’s enriched uranium is now buried and in effect inaccessible, but not eliminated. The US and Israel have indicated willingness to attack again if Iran tries to get back or rebuild.
Ultimately, the struggle between the world’s most sophisticated bunker-buster and Iran’s increasingly deepening tunnels is a battle of adaptation and counter-adaptation. As a Western intelligence official described it, “the new Natanz site may be even harder to destroy” than Fordow. The message for defense analysts is clear: engineering prowess, above and below, continues to influence the strategic calculus of the nuclear confrontation.
