The GBU-28 is a laser-guided bomb built by the United States for use against hardened targets (such as bunkers) during the first Gulf War. It is sometimes referred to as a bunker buster. Once the war began, the Air Force realized that then-current weapons were ineffective against deeply-buried and hardened (concrete-reinforced) structures, and asked defense contractor Texas Instruments for proposals. The GBU-28 was the result. Noteworthy for being designed, built, and put into operation in a 12 week period (unheard of in U.S. Defense procurement) the early GBU-28s were built out of surplus 8" howitzer barrels. The strong steel tubes were packed with over 600 lbs. of high explosive, fuzed, and given laser guidance units from the GBU-27 guided bomb. Later units were purpose-built rather than using the artillery tubes.
Once assembled, they were testing at the Tonopah Test Range and found to be capable of penetrating either 100 feet of earth or 20 feet of concrete and then properly detonating, thanks to their strong steel construction. Two were used during the Gulf War to attack buried command centers.
In 2005, Israel ordered 100 units of the GBU-28, its first foreign sale. Israel stated that Hezbollah command centers and rocket stockpiles were typically buried underground. The GBU-28 was designed to be dropped by either the F-111 Aardvark or the F-15E Strike Eagle. Israel flies Strike Eagles.
According to the Air Force, the weapon weighs approximately 4,300 lbs, is 25 ft. in length and has a diameter of between 14 inches and 2 ft. 4 inches in diameter, and can (if dropped from high enough altitude) reach targets 5 miles from its drop point. It is listed as costing approximately $145,000 per unit.