Unleashing unparalleled power, the GBU-72 bomb pierces hardened targets, detonating deep underground for devastating effect against fortified arsenals.
by Kris Osborn, Warrior
Sharp, penetrating contours, special steel alloys and pure “speed” are the key elements of bunker buster weapons, bombs engineered to cut through rock, earth and even concrete before “detonating” beneath the surface. These U.S. Air Force weapons, such as the GBU-28, have been part of the arsenal for years, yet the bomb-body and explosives technology has continued to advance.
Technological progress in the realm of “bunker-buster” earth penetrating weapons were used for the first time in combat against underground Iranian weapons stockpiles along the Strait of Hormuz. Its called the GBU-72, a new 5000-pound earth-penetrating bomb used recently for the first time in combat in the Iran war. Bunker busters are designed with sharpness for maximum penetration and descent into the earth at massive speeds, blasting through fortified rock and concrete through the sheer force of its size and 5,000-pound weight.
Delayed Fuse
The weapons use a time-delayed fuse to ensure the explosives don’t detonate until the weapon has reached its desired depth. This delay allows it to bypass outer layers of protection—such as bunker roofs or underground shielding—and explode within the target itself. The result is far more destructive than a surface blast, as the explosion occurs in confined spaces, amplifying pressure and structural damage.Its elongated, narrow body is engineered to minimize air resistance during descent and to concentrate force onto a smaller surface area upon impact. This focused force allows it to punch through layers of reinforced concrete, rock, or soil rather than dispersing energy across a wider area.
U.S. Central Command confirmed that indeed the GBU-72 was used against underground Iranian weapons, a circumstance which may have greatly reduced Iran’s coastal arsenal designed to launch attacks on ships transiting the Strait of Hormuz.
Detonating underground changes the nature of the blast dramatically. Instead of dispersing outward into open air, the energy is confined by the surrounding material. This confinement produces intense shockwaves and pressure that radiate through the structure. In underground missile facilities, these shockwaves can collapse tunnels, destroy storage chambers, and disrupt critical systems such as ventilation, power, and communications.
Underground Missiles
Missiles and their support equipment are particularly vulnerable to these effects. Even if the blast does not directly strike every stored weapon, the extreme pressure and structural failure can render them inoperable. Guidance systems, fuel lines, and electronic components are sensitive to shock and vibration. Additionally, collapsing tunnels can bury equipment under tons of debris, making recovery or use nearly impossible.
Another factor is accuracy. Modern bunker-buster bombs are often guided by satellite or inertial navigation systems, allowing them to strike precise locations. This precision is crucial when targeting underground facilities, as hitting the correct point—such as an entrance, a known storage chamber, or a structurally weaker section—maximizes the likelihood of successful penetration and destruction.
Bombs Penetrate Rock & Concrete
Many of these weapons are known to be capable of penetrating more than100 feet of earth and up to 22ft of rock and concrete, making them an optimal attack weapon for buried targets. Unlike general-purpose bombs that are designed to fragment on impact, the GBU-72 must remain intact long enough to burrow deep into a structure before detonating.
These kinds of weapons could prove defining in the ongoing war against Iran, given that multiple Should intelligence information be able to help Commanders identify the location of underground stockpiles of weapons, then precision-guided, heavy bunker buster weapons such as the GBU-72 may continue to be used to reduce the threat in the Strait of Hormuz.
Kris Osborn is President of Warrior Maven – Center for Military Modernization. Osborn previously served at the Pentagon as a highly qualified expert in the Office of the Assistant Secretary of the Army—Acquisition, Logistics & Technology. Osborn has also worked as an anchor and on-air military specialist at national TV networks. He has appeared as a guest military expert on Fox News, MSNBC, The Military Channel, and The History Channel. He also has a Masters Degree in Comparative Literature from Columbia University.