The GBU-57 massive ordnance penetrators, more commonly referred to as "bunker busters," that were used by the U.S. in strikes on Iranian nuclear facilities on June 22 were custom-designed for those specific targets after more than 15 years of intelligence gathering and weapons development, top Pentagon officials said Thursday. At a press briefing, Defense Secretary Pete Hegseth and Chairman of the Joint Chiefs of Staff General Dan Caine claimed that the weapons hit their intended marks precisely as planned.