Bunker Buster
Overview
Bunker Buster is a collective term for penetration-type bombs and related weapon systems designed to destroy hardened, buried targets such as enemy underground command posts, nuclear and missile facilities, and aircraft protection bunkers. Unlike conventional bombs that explode at the surface, bunker busters use high-strength warheads and delayed fuses to penetrate concrete and bedrock and detonate deep underground, destroying the interior of structures that surface detonations cannot reach. They became widely known to the public when the GBU-28 appeared during the 1991 Gulf War, and drew global attention again in June 2025 when the GBU-57 MOP was used in an attack on Iran's Fordow nuclear facility.
Main Content
Penetration Principle and Structure
The core of a bunker buster is not explosive power itself but kinetic energy and warhead material. The kinetic energy gained from falling or flight speed (1/2mv²) is concentrated on a narrow cross-section to pierce the target; for this purpose, thick casings made of high-strength steel alloys, tungsten, and sometimes depleted uranium alloys are used. In addition, a delayed fuse that delays detonation by several milliseconds so that the bomb does not explode immediately on impact is essential, and some warheads adopt a tandem method in which a leading shaped charge (free jet) bores an initial hole and the main warhead follows into it. Penetration against concrete is generally known to be about 3–5 times that against homogeneous rolled steel plate, but actual figures vary greatly depending on soil composition and impact angle.
Major Weapon Systems
- GBU-28: A 2,130 kg-class laser-guided penetration bomb developed in a short period during the 1991 Gulf War to target Iraq's Al-Tuwaitha air defense command bunker in Baghdad. It is known to penetrate about 30 m of earth or 6 m of concrete.
- GBU-57 MOP (Massive Ordnance Penetrator): A 13,600 kg (30,000 lb)-class weapon, of which up to two can be carried by the B-2 stealth bomber. It is known as the largest-class conventional penetration bomb, capable of penetrating about 60 m of concrete or 18 m of hardened rock.
- GBU-72 (A5K): A 2,270 kg-class new penetration bomb unveiled in 2021, having the character of a successor to the GBU-28.
- BLU-109: A 900 kg-class hardened penetration warhead, widely used in combination with various guidance kits.
- Storm Shadow / Taurus: Air-launched cruise missiles that strike underground command facilities from long range; the British Storm Shadow uses the BROACH tandem warhead, and the German Taurus KEPD 350 uses a 480 kg-class penetration warhead.
- B61-11: An earth-penetrating nuclear bomb, a concept that destroys deep bunkers using seismic effects.
Republic of Korea-Related Systems
The South Korean military operates bunker buster forces as part of the Kill Chain system targeting North Korea's underground command headquarters, tunnel artillery, and nuclear and missile facilities. Representative examples include the Taurus cruise missile (range of over 500 km) mounted on the Air Force's F-15K, Hyunmoo-series ballistic missiles carrying 2-ton-class warheads, and the Korean Tactical Surface-to-Surface Missile (KTSSM). However, penetration capability against very deep tunnel targets is continually pointed out as an area needing improvement.
Limitations and Controversy
Bunker busters have the limitations that ① accurate location and structural information on the target is required, ② conventional warheads are difficult to use against facilities buried tens to hundreds of meters deep, ③ penetration efficiency drops sharply when the ground is hard granite, and ④ effects are limited if the delayed fuse detonates prematurely at the surface. Accordingly, for deep targets, methods such as successively dropping multiple bombs on the same point, nuclear penetration bombs, or non-physical means such as cyber and special operations are considered in parallel.
Latest Trends
In June 2025, the United States deployed B-2 bombers in Operation 'Midnight Hammer' and dropped GBU-57s on Iran's Fordow, Natanz, and Isfahan nuclear facilities. The Fordow facility is known to be buried 80–90 m deep beneath a mountain, so an international debate continued over whether it was penetrated and the scale of the damage, with assessments by the IAEA and various national intelligence agencies diverging. Meanwhile, in the Ukraine war, the issue of providing Storm Shadow and Taurus became a political issue linked to the capability to strike Russian underground command facilities, and the United States is researching follow-on concepts to the GBU-57, new penetration bombs, and multiple-warhead sequential penetration techniques. In South Korea as well, development of heavy warheads and long-range systems to respond to very deep targets continues, and among the general public the term is also used figuratively to mean 'a decisive means of neutralizing a defensive shield.'
Related Topics
- [[GBU-57 MOP]]
- [[Penetration Bomb]]
- [[Taurus KEPD 350]]
- [[Kill Chain]]
- [[Delayed Fuse]]
- [[Storm Shadow]]