Key Points – The recent US “Operation Midnight Hammer” strike on Iranian nuclear facilities marked the first-ever combat use of the GBU-57 Massive Ordnance Penetrator (MOP), America’s most powerful non-nuclear weapon.
-According to the Pentagon, B-2 Spirit stealth bombers dropped 14 of the 30,000-pound “bunker buster” bombs on Iran’s deeply buried sites at Fordow, Natanz, and Isfahan. The GBU-57 is specifically designed to penetrate up to 60 meters of concrete before detonating its 5,300-pound warhead.
-While a full battle damage assessment is pending, officials state the strikes caused “extremely severe damage and destruction,” effectively “obliterating” Iran’s nuclear program for now.
Inside ‘Midnight Hammer’: A Look at the GBU-57 ‘Bunker Buster’
The recent American strikes on three Iranian nuclear infrastructure sites were as singular as they were destructive: Iranian facilities at Fordow, Natanz, and Isfahan suffered severe damage after 7 B-2 Spirit stealth bombers dropped 14 bunker-busting munitions on the sites.
Operation Midnight Hammer
The results were, in the eyes of the current American administration at least, very decisive. “Iran’s key nuclear enrichment facilities have been completely and totally obliterated,” President Donald Trump said in a Saturday night address at the White House.
“In total, US forces employed approximately 75 precision-guided weapons during this operation. This included, as the President stated last night, 14 30,000-pound GBU-57 Massive Ordnance penetrators, marking the first ever operational use of this weapon,” Chairman of the Joint Chiefs of Staff General Dan Caine told reporters during a Pentagon press briefing.
The United States called the strike on Iranian nuclear infrastructure Operation Midnight Hammer.
It marked the first operational use of the weapon in a real-world combat scenario.
“The US protection package employed high-speed suppression weapons to ensure safe passage of the strike package with fighter assets employing preemptive suppressing fires against any potential Iranian surface-to-air threats,” General Caine also told reporters on Sunday.
“We are currently unaware of any shots fired at the US strike package on the way in,” the general added.
GBU-57A/B Massive Ordinance Penetrator
The GBU-57 is currently the most powerful non-nuclear weapon in the American arsenal—it is also an enormous, 30,000-pound bunker-busting weapon designed to plunge deeply into the ground and penetrate even deeply buried, concrete-reinforced structures like those that protect Iran’s nuclear research and development facilities.
It was designed and built in the 2010s expressly to hold even the most deeply buried targets, like those in Iran, at risk. According to the US Air Force, it can penetrate 60 meters of concrete or 40 meters of earth and rock before detonating.
The bomb’s explosive payload alone is approximately 5,300 pounds, and given its enormous size, it is cleared for operational use only by the B-2 Spirit stealth bomber.
“Well, anything can happen in conflict. We acknowledge that, but the scope of this was intentionally limited,” Secretary of Defense Pete Hegseth said.
“That’s the message that we’re sending … Iran, in that sense, has a choice, but we’ve made it very clear to them, this is nuclear sites, this is nuclear capabilities. This is the line that the President set, and we set that back. Now is the time to come forward for peace.”
Although much of the speculation about the munitions’ efficacy centered on how deeply the weapon could penetrate underground, these analyses assumed that an explosive penetration would have to reach the same depth as underground facilities in order to destroy them, which is an incorrect assumption. A large explosion at depths close to buried infrastructure would likely be enough to severely damage underground targets without necessarily exploding at the precise depth.
“I know the battle damage is of great interest,” General Caine said, adding that “final battle damage will take some time, but initial battle damage assessments indicate that all three sites sustained extremely severe damage and destruction.”
A Numbers Game
Boeing, the manufacturer of the GBU-57, is believed to have produced at least 20 of the bunker-buster munitions. However, the exact number of highly specialized munitions built is neither known now nor likely to be disclosed in the future.
In any event, the GBU-57’s application to other operational scenarios is slim, and the need for a vast arsenal of these munitions is probably not very high.
The munition is specifically designed to hit hard-to-reach and very deeply buried targets. This operational requirement is very niche and perhaps most applicable to adversaries like Iran or North Korea. It bolsters the United States’ non-nuclear deterrence and offers some flexibility by providing remarkable destructive power while avoiding the politically sensitive nuclear threshold.
There are very few conceivable scenarios that would require the use of a munition like the GBU-57 Massive Ordinance Penetrator, aside from the North Korean and Iranian nuclear programs, both of which are deeply buried underground.
What the Iranian response will be exactly remains to be seen, though the regime has launched some munitions at American and American-allied targets in the Middle East.
What Happens Next?
What other scenarios would require these or similar munitions? Outside of important command bunkers or the nuclear facilities of other countries, their application would be rare otherwise, though they are strategically important.
In any event, it is not yet clear how successful the strikes were. Additional information would be necessary to determine efficacy.
About the Author: Caleb Larson
Caleb Larson is an American multiformat journalist based in Berlin, Germany. His work covers the intersection of conflict and society, focusing on American foreign policy and European security. He has reported from Germany, Russia, and the United States. Most recently, he covered the war in Ukraine, reporting extensively on the war’s shifting battle lines from Donbas and writing on the war’s civilian and humanitarian toll. Previously, he worked as a Defense Reporter for POLITICO Europe. You can follow his latest work on X.
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