Bunker Buster Bombs: Israel’s Request for US Deep-Penetration Weapons

Introduction

The ongoing Israel-Iran conflict has escalated dramatically in June 2025, with Israel launching “Operation Rising Lion” on June 13, targeting Iran’s nuclear facilities and military installations.

FAF, Defense.Forum analyzes the role of bunker buster bombs in this conflict, particularly regarding the GBU-57A/B Massive Ordnance Penetrator (MOP) and its potential use against Iran’s deeply buried Fordow nuclear facility.

The conflict represents a significant escalation from previous exchanges between the two nations.

The Current Israel-Iran War

Israel’s “Operation Rising Lion” began on June 13, 2025, with coordinated airstrikes against dozens of targets across Iran, including nuclear sites, military installations, and residential areas.

The Israeli Defense Forces (IDF) claimed to have damaged key nuclear sites and military installations, while Iran has retaliated with ballistic missiles and drone attacks under its own operation codenamed “True Promise III”.

Recent developments include

Israeli warplanes bombing approximately 20 locations in Tehran overnight on June 17-18, targeting missile production facilities

Mass evacuations from Tehran as civilians flee the capital

President Trump considering options that include joining Israel in attacking Iranian nuclear sites

Human rights groups reporting at least 585 people killed across Iran, including 239 civilians

Iran warning that U.S. intervention would risk “all-out war” in the region

GBU-57A/B Massive Ordnance Penetrator: Technical Analysis

Specifications and Capabilities

The GBU-57 MOP is currently the most powerful conventional bunker-busting weapon in the U.S. arsenal. Its key specifications include:

Weight

30,000 pounds (13,608 kg)

Length

20.5 feet (6.2 meters)

Diameter

31.5 inches

Explosive payload

5,342 pounds of high explosives, consisting of 4,590 pounds of AFX-757 and 752 pounds of PBXN-114

Guidance system

GPS/INS (Global Positioning System/Inertial Navigation System)

Penetration Capabilities

The GBU-57 MOP’s penetration capabilities are specifically designed for hardened underground targets:

Can penetrate up to 200 feet (61 meters) of reinforced concrete with a strength of 5,000 PSI

Can penetrate approximately 40 meters (125 feet) of moderately hard rock

Can penetrate about 8 meters (25 feet) of reinforced concrete with a strength of 10,000 PSI

Smart Fuze Technology

The bomb employs advanced detonation technology

Equipped with a Large Penetrator Smart Fuze (LPSF) that adjusts detonation timing based on impact depth and target characteristics

Features void-sensing fuzes that trigger detonation if a large cavity is detected within the bunker

Includes a delayed-action fuze allowing the warhead to survive initial impact before detonating

B-2 Spirit: The Only Delivery Platform

Aircraft Specifications

The B-2 Spirit stealth bomber is currently the only aircraft capable of delivering the GBU-57 MOP

Payload capacity

Over 40,000 pounds (18,144 kg) internally

Range

6,000 nautical miles (11,000 km) unrefueled, extending to over 10,000 nautical miles with aerial refueling

Maximum takeoff weight

336,500 pounds (152,634 kg)

Crew

Two (pilot and mission commander)

Power plant

Four General Electric F118-GE-100 turbofans, each producing 17,300 pounds of thrust

Operational Considerations

The B-2’s stealth capabilities make it uniquely suited for penetrating sophisticated air defense systems:

Low observability derived from reduced infrared, acoustic, electromagnetic, visual, and radar signatures

Can operate at altitudes up to 50,000 feet (15,000 meters)

Each B-2 can carry up to two GBU-57 MOPs per mission

The U.S. Air Force operates approximately 19 active B-2A aircraft

Current Deployment

The United States has forward deployed a significant portion of its B-2 fleet:

Approximately six B-2 bombers (about one-third of the total fleet) were deployed to Diego Garcia in the Indian Ocean in early 2025

This represents about half of the B-2s considered fully operational at any given time

Satellite imagery confirmed the presence of these bombers alongside refueling tankers

However, reports indicate they were “no longer visible by mid-June”

Iran’s Fordow Nuclear Facility

Strategic Importance

Fordow is considered Iran’s most critical and heavily fortified nuclear facility:

Houses Iran’s largest number of its most powerful centrifuges, according to the IAEA

Currently enriching uranium to 60% purity, just below the 90% weapons-grade threshold

Described by experts as “the heart of Iran’s nuclear programme”

Brett McGurk, who has served as Middle East coordinator for several American presidents, noted: “If you don’t get Fordow, you haven’t eliminated their ability to produce weapons-grade material”

Defensive Features

Fordow’s formidable defenses make it exceptionally difficult to target:

Depth

Built 80-110 meters (260-360 feet) underground within a mountain near Qom

Location

Approximately 100-160 kilometers south of Tehran

Geology

Protected by layers of hard sedimentary rocks including limestone and dolomite that absorb bomb impacts

Air defenses

Protected by Russian-made S-300 surface-to-air missile systems

Original purpose

Initially constructed as an Islamic Revolutionary Guard Corps missile base before being converted to a nuclear facility

Current Status

Despite Israel’s extensive strikes on other nuclear facilities, Fordow appears to have remained largely unscathed:

The IAEA has confirmed that Fordow was not damaged during Israel’s initial strikes

While Israel successfully damaged the Natanz facility and Isfahan’s uranium conversion facility, it “apparently failed to damage the underground Fordow Fuel Enrichment Plant”

The facility’s rock shielding renders it resistant to routine airstrikes

Israel’s Military Limitations

Current Bunker Buster Capabilities

Israel’s existing arsenal lacks the capability to effectively destroy Fordow

Israel possesses smaller bunker busters like the BLU-109 and GBU-28, but these can only penetrate a fraction of the depth required to reach Fordow’s core facilities

The BLU-109 can penetrate only about 1.8 meters of reinforced concrete

The GBU-28 can penetrate approximately 6 meters, still far short of Fordow’s depth

Mark Schwartz, a retired U.S. Army lieutenant general and Rand Corporation researcher, stated: “Only the United States has the conventional capacity to obliterate Fordo”

Potential Alternative Approaches

Some Israeli officials have suggested alternative strategies for targeting Fordow:

A senior Israeli military official recently told The Wall Street Journal that Israel possesses both a strategy and operational capacity to target Fordow independently

Ehud Eilam, a former researcher for Israel’s Ministry of Defense, outlined potential approaches including deploying numerous smaller penetrating munitions to burrow into Fordow’s defenses

Other options might include high-risk special operations missions, cyber warfare, or targeted assassinations of key personnel

However, military analysts maintain that the American-made GBU-57 remains the most promising option for neutralizing the facility

U.S. Strategic Considerations

Current U.S. Posture

The United States under President Trump appears to be weighing military options while pursuing diplomatic solutions:

Trump has threatened Iran with “bombing the likes of which they have never seen before” if Tehran does not sign a deal on its nuclear program

The deployment of B-2 bombers to Diego Garcia is viewed as a strategic message to Iran

Trump reportedly cut short his appearance at the G7 summit to attend a National Security Council meeting on the Middle East crisis

The White House announced that Trump would depart the G7 summit earlier than planned due to the escalating situation in the Middle East

Potential for U.S. Intervention

Several factors suggest the U.S. is preparing for possible military action:

Reports indicate that a National Security Council meeting debated a possible strike on Iran’s Fordow nuclear facility

Trump stated at the G7 Summit: “Iran will not win in this battle” and called on Tehran to return to negotiations “before it’s too late”

Trump has been engaged in nuclear negotiations with Iran while simultaneously building up military pressure

The president commented: “I think Iran is at the negotiating table, they want to make a deal”

Implications of Potential Fordow Strike

Regional and Global Consequences

A successful strike on Fordow would have far-reaching implications:

Nuclear program setback

Would cripple Iran’s most secure uranium enrichment facility, potentially setting back its nuclear program by years

Escalation risk

Iran has warned that U.S. intervention would risk an “all-out war” in the region

Civilian impact

Thousands of people are already fleeing Tehran amid the current airstrikes

Diplomatic fallout

Iran might withdraw from the Nuclear Non-Proliferation Treaty, ending international inspections

Oil market disruption

Escalation in the Gulf region would likely cause oil prices to spike

Historical Precedents

Previous strikes on nuclear facilities provide context for potential outcomes:

Israel’s 1981 bombing of Iraq’s Osirak reactor (Operation Opera) delayed Iraq’s nuclear ambitions but led to international condemnation

Israel’s 2007 destruction of a suspected Syrian nuclear reactor set back Syria’s program but raised questions about the use of force

These precedents suggest that while military strikes can delay nuclear programs, they rarely eliminate the underlying knowledge or motivation

Conclusion

The current Israel-Iran conflict has reached a critical juncture, with Israel’s “Operation Rising Lion” targeting Iran’s nuclear infrastructure but unable to neutralize the deeply buried Fordow facility

The GBU-57 MOP, deliverable only by American B-2 bombers, represents the sole conventional weapon capable of potentially destroying this hardened target.

President Trump’s decision on whether to authorize the use of this weapon or provide it to Israel will likely determine the trajectory of the conflict.

Such a decision would represent a significant escalation, potentially drawing the United States into direct conflict with Iran while fundamentally altering the strategic balance in the region.

As thousands flee Tehran and both sides exchange missile strikes, the international community watches closely to see whether diplomatic efforts will prevail or if the conflict will escalate further into what Iran has warned could become an “all-out war”