The US military did not use a GBU-57 bunker-buster Massive Ordnance Penetrator (MOP) bomb on Iran’s Isfahan nuclear facility because the site is so deep that the MOP would have been ineffective, the US’s top general told senators.

According to CNN, the comment by Gen. Dan Caine, which was described by three people who listened to his remarks and a fourth who was briefed on them, is the first known reason shared by the US military for not using the GBU-57 MOP at the Isfahan nuclear site.

US officials believe Isfahan’s underground structures house nearly 60% of Iran’s enriched uranium stockpile.

US B-2 bombers launched over a dozen GBU-57s on Iran’s Fordow and Natanz nuclear sites; however, Isfahan was attacked by submarine-launched Tomahawk missiles.

Earlier, Caine told journalists the strikes involved more than 125 US aircraft, including B-2 Spirit stealth bombers, fighters, aerial refueling tankers, a guided missile submarine, and intelligence, surveillance, and reconnaissance aircraft.

“This mission demonstrates the unmatched reach, coordination, and capability of the United States military,” the general said. “No other military in the world could have done this.”

The US employed seven B-2s in the strikes — aircraft that can fly 6,000 nautical miles (9,600 kilometers) without refueling and which are designed to “penetrate an enemy’s most sophisticated defenses and threaten its most valued, and heavily defended, targets,” according to the US military.

“This was the largest B-2 operational strike in US history and the second-longest B-2 mission ever flown,” according to Caine.

In addition to the bombers, a US guided missile submarine in the Middle East launched more than two dozen missiles at unspecified “surface infrastructure targets” at Isfahan, one of three nuclear sites struck in the operation, Caine said.

The missiles are “designed to fly at extremely low altitudes at high subsonic speeds, and are piloted over an evasive route by several mission-tailored guidance systems” and were first used in 1991 against Iraqi forces during Operation Desert Storm, according to the US military.

Impact Of Strikes

Meanwhile, the Trump administration has insisted that the operation against Iranian nuclear facilities was a total success, criticizing journalists for reporting on an intelligence assessment that took a more conservative line.

President Donald Trump “created the conditions to end the war, decimating — choose your word — obliterating, destroying Iran’s nuclear capabilities”, Defense Secretary Pete Hegseth told journalists at the Pentagon.

Trump himself has called the strikes a “spectacular military success”, insisting they “obliterated” the nuclear sites, setting Iran’s programme back by “decades”.

Earlier this week, however, US media reported on a leaked preliminary US intelligence assessment that said the strikes had only set back Iran’s nuclear programme by months — coverage sharply criticized by Hegseth and others.

The document was “leaked because someone had an agenda to try to muddy the waters and make it look like this historic strike wasn’t successful”, Hegseth said.

He also highlighted a statement by CIA chief John Ratcliffe, who pointed to a “historically reliable and accurate” source of information indicating that “several key Iranian nuclear facilities were destroyed and would have to be rebuilt over the course of years”.

Israel Happy

The Israeli military has said it had delivered a “significant hit” to Iran’s nuclear programme.

While it stated that its attacks had delayed the programme “by several years,” it also noted that it was “still early to assess the results of the operation.”

Israeli Prime Minister Benjamin Netanyahu hailed a “historic victory” in the 12-day conflict and vowed to thwart “any attempt” by Iran to rebuild its nuclear programme.

Meanwhile, Iran’s supreme leader, Ayatollah Ali Khamenei, has hailed what he described as Iran’s “victory” over Israel.

“The American president exaggerated events in unusual ways,” Khamenei said, insisting the strikes had done “nothing significant” to Iran’s nuclear infrastructure.

Iran’s Foreign Minister, Abbas Araghchi, however, called the damage “serious” and stated that a detailed assessment was underway.

Doubts remain about whether Iran quietly removed more than 400 kilogrammes (880 pounds) of uranium enriched to 60 percent from its most sensitive sites before the strikes — to hide it elsewhere in the country.

The stockpile could, in theory, produce more than nine atomic bombs — if the enrichment level were raised to 90 percent.

A Khamenei adviser, Ali Shamkhani, has said that the country still had its nuclear stockpile.

“Even if nuclear sites are destroyed, the game isn’t over; enriched materials, indigenous knowledge, and political will remain,” he said in a post on X.

UN nuclear watchdog the International Atomic Energy Agency (IAEA), has called for its inspectors to be able to return to Iran’s nuclear sites in a bid to account for the stockpiles.

However, on Thursday, the Iranian body tasked with vetting legislation approved a bill passed by lawmakers that suspends cooperation with the IAEA. That will go to Iran’s president for final ratification.

All sides, even some voices in Tehran, agree that the strikes on Fordo, Natanz, and Isfahan caused major damage.

“I believe annihilated is too strong. But it (Iran’s nuclear programme) has suffered enormous damage,” IAEA head Rafael Grossi told French radio RFI.

“It is true that, with its reduced capacities, it will be much more difficult for Iran to continue the pace it had.”

Thousands of centrifuges — the machines used to enrich uranium — were no longer operational, he said, “given the explosive payload utilised and the extreme vibration-sensitive nature” of the equipment.

Experts say that some centrifuges were stored in unknown locations in recent years, as Iran’s cooperation with the UN agency deteriorated.

Other sites of the nuclear programme remain intact.