WASHINGTON (AP) — Pentagon leaders laid out new details Thursday about military tactics and explosives to bolster their argument that U.S. attacks had destroyed key Iranian nuclear facilities, but little more emerged on how far back the bombing had set Tehran’s atomic program.

In a rare Pentagon news briefing, Defense Secretary Pete Hegseth and Gen. Dan Caine, chairman of the Joint Chiefs of Staff, worked to shift the debate from whether the nuclear targets were “obliterated,” as President Donald Trump has said, to what they portrayed as the heroism of the strikes as well as the extensive research and preparation that went into carrying them out.

“You want to call it destroyed, you want to call it defeated, you want to call it obliterated — choose your word. This was an historically successful attack,” Hegseth said in an often combative session with reporters.

It was the latest example of how Trump has marshaled top administration officials to defend his claims about the effectiveness of the U.S. strikes. At stake is the legacy of the Republican president's intervention in the brief war between Israel and Iran, as well as the future of American foreign policy toward Iran.

Pentagon gives little detail on status of Iran's highly enriched uranium

Hegseth appeared less confident that the strikes got all of Iran's highly enriched nuclear material.

Asked repeatedly whether any of it was moved to other locations before the U.S. attack, Hegseth acknowledged that the Pentagon was “looking at all aspects of intelligence and making sure we have a sense of what was where."

He added, “I’m not aware of any intelligence that says things were not where they were supposed to be” or that they were moved.

Satellite imagery showed trucks and bulldozers at Iran’s Fordo uranium enrichment site, the main target of the bombings, days before the strikes, which occurred between 6:40 p.m. and 7:05 p.m. EDT Saturday. Experts said enriched uranium stocks can be moved in small canisters and are hard to find.

“It would be extremely challenging to try and detect locations where Iran may be hiding highly enriched uranium,” said Kelsey Davenport, director of nonproliferation policy at the nonpartisan Arms Control Association.

Trump expressed confidence that uranium was not pulled out before the attack.

“Nothing was taken out of facility,” he said on social media. “Would take too long, too dangerous, and very heavy and hard to move!”

New details emerge on how the U.S. carried out the attacks

U.S. stealth bombers dropped 12 deep penetrator bombs, called bunker busters, on Fordo and two on the Natanz site, a U.S. official told The Associated Press. The official spoke on the condition of anonymity to discuss military operations.

Hegseth and Caine described 15 years of study and planning going into the bombing mission and they showed video of a test explosion of a “bunker buster” munition, designed to penetrate deep into mountains.

While Hegseth, a former Fox News anchor, spent the bulk of his time slamming the media coverage and personally insulting reporters who questioned him, Caine stuck to the military details of the bombing.

Caine said the U.S. targeted the ventilation shafts at the Fordo facility as the entry point for the bombs. In the days before the U.S. attack, the Iranians placed large concrete slabs on top of both ventilation routes from the underground facilities to try to protect them, he said.

He said the first bomb dropped was used to eliminate the concrete slab, and then four of the bombs were dropped down the main shaft with slightly different angles to take out various parts of the underground facility.

The pilots of the bombers described the flash after the bomb drop as “the brightest explosion they had ever seen,” Caine said.

He noted it is not his job to do the assessment of the damage. Asked if he has been pressured to provide a more optimistic view of the results, Caine said no.

“I’ve never been pressured by the president or the secretary to do anything other than tell them exactly what I’m thinking. And that’s exactly what I’ve done,” he said.

Caine also lauded the troops who remained at Al Udeid Air Base in Qatar when the Iran launched its counterattack Monday. He said just 44 soldiers stayed to operate the two Patriot missile batteries and protect the entire air base.

“You know that you’re going to have approximately two minutes, 120 seconds, to either succeed or fail,” Caine said, adding, “They absolutely crushed it.”

Hegseth dismisses initial assessment from the Pentagon’s own intelligence agency

Hegseth repeated assertions that an early assessment from the Defense Intelligence Agency, a part of the Defense Department, was preliminary and that the report acknowledged there was low confidence and gaps in information.

Hegseth repeatedly scolded reporters for “breathlessly” focusing on that assessment and said such stories were just attempts to undermine Trump.

That report said that while the U.S. strikes on three Iranian nuclear facilities did significant damage, the sites were not totally destroyed and that Tehran's program was only set back by a few months.

Hegseth and others have not disputed the contents of the DIA report but have focused on a CIA statement and other intelligence assessments, including those out of Iran and Israel, that said the strikes severely damaged the nuclear sites and rendered the enrichment facility inoperable.

The International Atomic Energy Agency is not now able to assess the exact damage to the Fordo site, but the centrifuges there are “no longer operational,” the U.N. nuclear watchdog's chief, Rafael Mariano Grossi, told Radio France Internationale on Thursday.

Trump appeared buoyed by Hegseth’s fierce display of loyalty and his repeated attacks on news organizations during the briefing. The president said on social media that it was "one of the greatest, most professional, and most ‘confirming’ News Conferences I have ever seen!”

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Associated Press writers Eric Tucker, Chris Megerian and Ellen Knickmeyer contributed to this report.