The Pentagon on Thursday released new details about how the US prepared for its marathon bombing mission against three Iranian nuclear sites, the crews that carried out the daring weekend raid, and how Iran tried fortifying one of the sites that held critical aspects of its nuclear program.

In a morning briefing, which President Donald Trump had promised ahead of time would be “interesting and irrefutable,” Defense Secretary Pete Hegseth said the US undertook “the most secret and most complex military operation in history,” without offering many specifics. It was Joint Chiefs of Staff Chairman Gen. Dan Caine who laid out compelling details on how the the highly sophisticated mission was conducted.

The briefing, however, did not provide new intelligence supporting the president’s assertion that the strikes “obliterated” Iran’s nuclear program.

Caine revealed previously unpublicized details about the bombing crew that took part in the mission, as well as the extensive preparations undertaken for it across the military.

So many experts worked on designing the bombs that hit their target that they became the “biggest users of supercomputer hours within the United States of America” at one point, he said.