GBU-57 GBU-57A/B MOP bunker-buster bomb.

The GBU-57A/B MOP (Massive Ordnance Penetrator) is an air-launched, precision-guided bunker-buster bomb designed by the American Company Boeing to conduct strategic deep-target engagement. Originating from post-2003 military assessments, the bomb was developed to overcome the limitations of previous bunker-busting munitions, especially against adversaries using hardened subterranean facilities for critical assets such as WMDs and command centers.

A bunker-buster weapon system is specifically engineered to destroy hardened and deeply buried targets (HDBTs) through kinetic penetration followed by delayed internal detonation. These weapons rely on a dense, hardened casing and a high-velocity impact to breach concrete or rock before initiating an internal explosive event.

The GBU-57’s development began in the early 2000s under the U.S. Defense Threat Reduction Agency, with an urgent need for a heavy penetrating weapon that could reach and neutralize targets protected by reinforced concrete and natural rock formations. In 2009, Boeing was tasked with final integration, leading to the weapon’s operational deployment in 2011. The GBU-57A/B became a central part of the U.S. Air Force’s strategic strike capabilities.

The weapon’s first confirmed combat use occurred on June 22, 2025, during American airstrikes on Iranian nuclear installations at Fordow, Natanz, and Isfahan. Conducted in the early hours, the raid saw the deployment of multiple GBU-57 bombs from B-2 Spirit stealth bombers. Reports vary, citing between five and six bombs used, with some accounts suggesting up to twelve dropped on Fordow and an additional two on Natanz. The operation demonstrated the MOP’s unparalleled capacity to defeat deeply buried, hardened military facilities.

- GBU-57/B: Original variant with BLU-127/B warhead
- GBU-57A/B: Enhanced production variant with improved internals
- GBU-57B/B: Features refined guidance and fuze systems
- GBU-57C/B: Variant with additional (undisclosed) performance improvements
- GBU-57D/B: Incorporates smart fuze for optimized internal detonation
- GBU-57E/B: Enhanced Target Reach (ETR-IV) configuration with BLU-127C/B warhead
- GBU-57F/B: Most recent variant with classified upgrades