 In three weeks, a cooperative effort directed by the Armament Systems Division at Eglin Air Force Base in Florida developed the GBU-28 that was used successfully by F-111Fs against a deep underground complex not far from Baghdad just before the end of the war.The United States has developed a Massive Ordnance Penetrator, designed to attack very deeply buried targets without the use of nuclear weapons with the inherent huge levels of radioactive pollution and their attendant risk of retaliation in kind.Anglo-American bomb tests (Project Ruby) on the comparative effectiveness of large bombs against reinforced concrete structures were carried out in 1946.