From Development to Deployment: The GBU-57 MOP’s Journey from Eglin AFB to Iran

In June 2025, when B-2 Spirit bombers dropped 14 Massive Ordnance Penetrator (MOP) bombs on Iran’s deeply buried nuclear facilities, it marked the culmination of a development journey that began in the early 2000s.

I visited Eglin Air Force Base in 2010 and witnessed the weapon’s development firsthand; for me, the recent strikes represented the ultimate validation of a prescient strategic vision.

During a  2010 visit to Eglin Air Force Base, the scale and scope of the Air Armament Center’s mission became immediately apparent. Under the leadership of Major General C.R. Davis, who served as both AAC Commander and USAF PEO for Weapons, Eglin had positioned itself as the epicenter of American weapons development — a place where, in Davis’s words, synergy between concept, deployment, and logistics support created “a formidable capability to shape an integrated weapons development process.”

The portfolio of weapons under development at Eglin in 2010 painted a picture of anticipated future conflicts. Among the systems being developed was “the Massive Ordnance Penetrator (MOP) designed for destroying hardened targets with the use of conventional ordnance.” At the time, this seemed like one item among many in an impressive arsenal that included JASSM, MALD/J, various Small Diameter Bomb variants, and AMRAAM.

What wasn’t immediately apparent to visitors in 2010 was how specifically the MOP was being tailored for one particular target set: Iran’s emerging nuclear infrastructure.

By 2010, the strategic calculus driving MOP development had crystallized around a specific challenge. Iran, learning from Israel’s successful strikes on Iraq’s Osirak reactor in 1981 and Syria’s nuclear facility in 2007, had embarked on a different approach to nuclear development. Rather than building vulnerable above-ground facilities, Iran was constructing its most critical nuclear infrastructure deep underground, protected by hundreds of feet of rock and reinforced concrete.

The Fordow facility, built into a mountainside near Qom, epitomized this strategy. Construction had begun around 2006-2007, and by 2010 — when I was touring Eglin — it was nearing operational status. Intelligence estimates suggested the facility was buried 260-300 feet underground, far deeper than any existing bunker-buster could reach.

This created what Major General Davis described in 2010 as a fundamental challenge in weapons development: “This process must start with future target set playing a key role in leading the design process. The process must not start with a set of constraints defined by specific legacy platform dimensions.”

Iran’s Fordow facility represented exactly this kind of target-driven requirement. No existing weapon could reach it, which meant developing an entirely new class of munition.

The Development Timeline: From Concept to Combat

The GBU-57 MOP’s development history reveals a weapon system specifically engineered for the Iran challenge:

• 2004: Following lessons learned from Iraq’s bunker-busting operations, the Defense Threat Reduction Agency launched the MOP project, with the Air Force asking contractors to develop a 30,000-pound precision-guided bomb for deep underground targets.
• 2005-2007: Boeing completed concept refinement and detailed design phases, with the weapon’s specifications clearly targeting Iranian-type facilities.
• 2007: The first static detonation test at White Sands Missile Range validated the weapon’s explosive capabilities.
• 2008-2010: Flight testing phase using B-52 bombers (though the weapon would ultimately be B-2 exclusive).
• During this entire period, Iran’s Fordow facility was under construction, creating a real-time arms race between American penetrator technology and Iranian defensive engineering.

Strategic Anticipation: Davis’s Vision Realized

Major General Davis’s 2010 reflection on weapons development proves remarkably prescient: “We could have anticipated that this weapon was going to be needed now, or very close to now, if we had done things a little bit differently, five or six years ago.”

In the case of the MOP, the anticipation was exactly right. The weapon system was developed specifically with Iran’s nuclear program in mind, and when diplomatic efforts failed to prevent Iran’s nuclear advancement, the military option was ready.

Davis had identified four key elements for the Air Force’s future roadmap: air dominance, long-range strike, hardened and deepened targets, and close controlled strike. The MOP represented the solution to “hardened and deepened targets”— a capability that proved essential 15 years later.

The 2025 Validation: Operation Midnight Hammer

When B-2 bombers launched from Whiteman Air Force Base in Missouri on June 21, 2025, they carried 14 GBU-57 MOPs —  targeted at Fordow and 2 at Natanz. The operation, dubbed “Midnight Hammer,” represented the first combat use of a weapon that had been in development for over two decades.

The targeting was precise and deliberate. Fordow, the facility that had driven much of the MOP’s development requirements, received the majority of the weapons. Intelligence had long assessed that only the MOP had the capability to penetrate Fordow’s mountain protection and reach the underground centrifuge halls.

General Dan Caine, Chairman of the Joint Chiefs of Staff, described the results as “extremely severe damage,” though satellite imagery suggests the facilities weren’t completely destroyed — a reminder that even the most sophisticated weapons face limitations against the most hardened targets.

Lessons for Future Weapons Development

The MOP’s development and employment offer several insights for future weapons programs:

• Target-Driven Requirements Work: By starting with Iran’s specific defensive measures and working backward to weapon requirements, the MOP program delivered a capability precisely suited to its intended mission.
• Integration Challenges Matter: The MOP’s exclusive integration with the B-2 bomber limited employment options but ensured the system could reach heavily defended targets. This trade-off proved acceptable given the weapon’s specialized mission.
• Anticipation Pays Dividends: Major General Davis’s emphasis on anticipating future needs rather than reacting to current ones proved prophetic. The MOP was ready when diplomacy failed.

Conclusion: From Eglin’s Drawing Boards to Iran’s Mountains

The journey from Eglin AFB’s development facilities to Iran’s nuclear sites represents modern weapons development at its most strategic. What began as recognition of a capability gap became a two-decade development effort that culminated in the world’s most powerful conventional bunker-buster finding its intended target.

The recent strikes provide a sobering reminder of being ready for a mission but delaying it based on political dynamics. The engineers and program managers working on the MOP weren’t just developing another weapon — they were crafting a specific solution to a specific strategic challenge that they correctly anticipated would eventually require military resolution as early as 2010.

The synergy that Major General Davis described at Eglin — between concept development, testing, production, and strategic planning — proved its worth in the skies over Iran. The weapon developed to counter Iran’s nuclear ambitions ultimately found its target, validating both the strategic vision and the patient, methodical approach to weapons development that defines American military’s capabilities.

Whether the MOP strikes will achieve their strategic objective of halting Iran’s nuclear program remains to be seen. But there’s no question that when the moment came, the right weapon was ready — precisely because the right people at the right place had anticipated this moment 15 years earlier and were ready then waiting for the right political circumstances.

Featured image: Weapon specialists gather in front of a mock up of the Massive Ordnance Penetrator and the B-2 weapons load trainer Dec. 18 at Whitman Air Force Base, Mo. U.S. Air Force photo.