Saturday’s US strike on Iran’s Fordow nuclear fuel enrichment plant was 15 years in the making, Chairman of the Joint Chiefs of Staff Lt. Gen. Dan Caine said Thursday — revealing that the heavy-duty bunker bombs used were designed specifically for the deeply buried site.

The US first learned in 2009 of the presence of the Fordow plant, which is cut about half a mile into the side of a mountain.

Officials and a Defense Threat Reduction Agency (DTRA) officer briefed on the subject quickly determined that the US did not have a “weapon that could adequately strike and kill this target,” Caine said.

So they began construction of the 30,000-pound GBU-57 series MOP (Massive Ordnance Penetrator) bunker-busters, all while everyday Americans had no clue of the threats Tehran posed.

“Weaponeering is the science of evaluating a target,” Caine said. “… Ultimately, weaponeering is determining the right weapon and fuse combination to achieve the desired effects and maximum destruction against a target.” 

“In the case of Fordow, the DTRA team understood with a high degree of confidence the elements of the target required to kill its functions and the weapons were designed, planned and delivered to ensure that they achieve the effects in the mission space.”

At one point, Caine added, “we had so many PhDs working on the MOP program doing modeling and simulation that we were — quietly and in a secret way — the biggest users of supercomputer hours within the United States of America.”

Together, the Pentagon worked with industry and other tacticians to develop the GBU-57 — which can only be dropped by B-2 bombers — testing it “over and over again.”

“(They) tried different options, tried more after that, they accomplished hundreds of test shots and dropped many full scale weapons against extremely realistic targets for a single purpose: kill this target,” the chairman said.

The largest bomb in the Pentagon’s arsenal, the GBU-57 is “comprised of steel, explosive and a fuse programmed specifically for each weapon to achieve a particular effect inside the target,” Caine went on.

“Each weapon had a unique desired impact, angle, arrival, final heading and a fuse setting,” he said. “The fuse is effectively what tells the bomb when to function. A longer delay in a fuse, the deeper the weapon will penetrate and drive into the target.”

With the benefit of 15 years of intelligence analysis, the Pentagon designed Saturday’s strike to Fordow’s specifications — targeting two ventilation shafts that would funnel the bunker busters deep inside plant.

“The Iranians attempted to cover the shafts with concrete to try to prevent an attack,” Caine said. “The planners had to account for this — they accounted for everything. The [concrete] cap was forcibly removed by the first weapon and the main shaft was uncovered.”

Additionally, four bombs had to enter the main exhaust shaft, “move down into the complex at greater than 1000 feet per second and explode in the mission space.”

Caine said he spoke Wednesday with two DTRA officers who had spent “their life’s work” designing the bombs dropped on Fordow.

“One of them said, ‘I can’t even get my head around this. My heart is so filled with the pride of being a part of this team. I am so honored to be a part of this,’” Caine said. “To you both, thank you and thank you to your families. 

“Operation Midnight Hammer was the culmination of those 15 years of incredible work, the air crews, the tanker crews, the weapons crews that built the weapons, the load crews that loaded it.”