The United States military has many munitions in its arsenal. From nuclear-armed intercontinental ballistic missiles to the AGM-114 Hellfire air-to-ground missile, the U.S. military has hundreds of weapon systems with different destructive capabilities for different missions.

But when it comes to destroying enemy underground bunkers without using nuclear weapons, there is only one weapon: the GBU-57A/B Massive Ordnance Penetrator (MOP).

This massive munition weighs 30,000 pounds and is the largest and most powerful non-nuclear bunker bomb in the world.

The GBU-57A/B MOP: A Monster of a Bomb

The GBU-57A/B MOP has one simple mission: take out enemy underground bunkers. The massive bomb can reach and destroy hardened concrete and steel bunkers located deep underground.

“The Massive Ordnance Penetrator (MOP) is a weapon system designed to accomplish a difficult, complicated mission of reaching and destroying our adversaries’ weapons of mass destruction located in well protected facilities,” the U.S. Air Force states about the massive MOP.

In addition to its massive weight (over 12 tons), the GBU-57A/B MOP is quite large with a length of 20.5 feet (for comparison, an F-16 Fighting Falcon fighter jet is 49 feet long) and a diameter of 31 inches. The bomb carries a warhead that weighs about 5,350 pounds. Overall, the munition can penetrate 200 feet and reach even the most protected underground facilities.

The GBU-57A/B MOP is additionally special because there is only one aircraft in the U.S. military capable of carrying it to battle: the B-2 Spirit. The Air Force also wants to fit the munition to the B-21 Raider stealth bomber that will succeed the B-2 in the near future.

In the event of a near-peer conflict with China or Russia, or a war with North Korea or Iran, America’s adversaries would seek to hide their command and control elements underground in an attempt to avoid the deadly gaze of the U.S. military. And for a good reason. The deeper underground, the harder to eliminate. That is why militaries are storing their nuclear warheads and other precious military hardware and capabilities deep underground. But the GBU-57A/B MOP could potentially reach that far and destroy the bunker. And even if it can’t reach the bunker itself, the sheer force of a 30,000 bomb could easily block passages and destroy communication lines from the bunker to the surface.

Tests on the GBU-57A/B MOP began in 2004. In 2008, the Air Force started conducting flight tests. Boeing, the manufacturer, delivered the first bombs in 2011.

To develop the munition, the Air Force worked with the Defense Threat Reduction Agency (DTRA), with the Air Force providing funding and management of the program and DTRA supporting it.

Although the exact number of munitions is classified, the Air Force has at least twenty GBU-57A/B MOPs in its arsenal. If it came to blows with a near-peer adversary like China or Russia, that number seems rather low. However, the Air Force does have other weapons to fill the gap, even if they aren’t as destructive as the massive MOP.

Stavros Atlamazoglou is a seasoned defense journalist specializing in special operations and a Hellenic Army veteran (national service with the 575th Marine Battalion and Army HQ). He holds a BA from Johns Hopkins University and an MA from the Johns Hopkins School of Advanced International Studies (SAIS). His work has been featured in Business Insider, Sandboxx, and SOFREP.