Air Force drops 14 MOP bombs on Iranian nuclear sites during first operational use of the weapon

U.S. Air Force B-2 Spirit stealth bombers dropped a total of 14 “massive ordnance penetrator” bombs on Iranian nuclear sites during Operation Midnight Hammer early Sunday local time, according to senior officials.

The event marked the first-ever operational employment of the weapon, Secretary of Defense Pete Hegseth confirmed Sunday during a press briefing at the Pentagon.

The 30,000-pound GBU-57 bomb, also known as the MOP, is designed to be capable of attacking underground targets. It can reportedly hit locations hundreds of feet below ground level.

“MOP is a large, GPS-guided, penetrating weapon with the ability to attack deeply-buried and hardened bunkers and tunnels. The warhead case is made from a special high‑performance steel alloy and its design allows for a large explosive payload while maintaining the integrity of the penetrator case during impact,” according to an Air Force description of the system.

Due to the bomb’s size and design, it can only be carried by the B-2 bomber. Each B-2 can carry two GBU-57s.

Early testing of the MOP began about 20 years ago under a technology demonstration effort led by the Defense Threat Reduction Agency before the technology was transitioned to an Air Force “quick reaction capability program,” according to a service fact sheet. Boeing was contracted in 2009 for MOP-aircraft integration efforts. In 2017, the MOP transitioned to an Air Force program of record, according to a report by the Pentagon’s director of operational test and evaluation.

Notably, in fiscal 2024, the Air Force conducted two full-scale tests to “verify fixes to a B-2 integration issue,” according to a DOT&E annual report.

The Air Force has been pursuing a MOP modification program to integrate a “smart fuze” capability into the weapon. The so-called Large Penetrator Smart Fuze is intended to provide “increased probability of kill” against hard and deeply buried targets “by mitigating the risk of target intelligence uncertainty,” according to the DOT&E report. Defense officials on Sunday did not say whether the MOPs used in Midnight Hammer were equipped with the smart fuze capability.

Seven B-2s and a variety of other assets were involved in Midnight Hammer, which included U.S. attacks on Fordow, Natanz and Esfahan in Iran, Gen. Dan Caine, chairman of the Joint Chiefs of Staff, told reporters at Sunday’s press briefing.

Hegseth said the aim of the mission, which was ordered by President Donald Trump, was to “destroy or severely degrade” Iran’s nuclear program. Western officials were concerned that the Iranian regime could use the country’s nuclear materials and know-how to build weapons of mass destruction.

“At approximately 6:40 p.m. Eastern Standard Time, 2:10 a.m. Iran time, the lead B-2 dropped two GBU-57 Massive Ordnance Penetrator weapons on the first of several aim points at Fordow,” Caine said. “The remaining bombers then hit their targets as well, with a total of 14 MOPs dropped against two nuclear target areas. All three Iranian nuclear infrastructure targets were struck between 6:40 p.m. and 7:05 p.m. Eastern time … with the Tomahawk missiles [launched from a submarine] being the last to strike at Esfahan to ensure we retain the element of surprise throughout the operation. Following weapons release, the Midnight Hammer strike package exited Iranian airspace, and the package began its return home.”

Fighter jets went in ahead of the bombers to guard against enemy fighter aircraft and surface-to-air missiles. The Defense Department is unaware of any shots being fired at the U.S. military aircraft on their way in or out of Iran, Caine noted.

About 75 precision guided weapons were employed during the operation, including the 14 MOPs, according to Caine.

Dozens of air refueling tankers were also involved in the mission, he noted, as well as intelligence, surveillance and reconnaissance aircraft, and hundreds of maintenance and operational personnel.

On Sunday evening, Trump posted on Truth Social that the B-2 pilots who took part in Midnight Hammer had safely returned to their base in Missouri. The mission from Whiteman Air Force Base to Iran and back lasted about 36 hours, with the help of aerial refueling, according to U.S. Strategic Command.

Senior U.S. officials touted the operation as a success.

“The damage to the Nuclear sites in Iran is said to be ‘monumental.’ The hits were hard and accurate. Great skill was shown by our military,” Trump said in a Truth Social post.

Hegseth described the mission as an “incredible and overwhelming success.”

Caine noted that a final battle damage assessment will take “some time” to complete. However, initial battle damage assessments “indicate that all three sites sustained extremely severe damage and destruction,” he told reporters.

Officials in the Trump administration have said they now hope to have a negotiated settlement to the conflict. It remains to be seen how Iran will respond.