It's 20-feet long, weighs 30,000 pounds and is capable of penetrating 200 feet deep inside a target and then exploding.

GBU-57/B—also known as a Massive Ordnance Penetrator (MOP)—was a solution. Its Air Force fact sheet sums it up as “a weapon system designed to accomplish a difficult, complicated mission of reaching and destroying our adversaries' weapons of mass destruction located in well protected facilities.”

The 30,000-pound MOP represents the largest conventional bomb in the U.S. arsenal, specifically engineered to defeat hardened underground bunkers. Its massive size requires the B-2 to carry only one or two MOPs per mission, but provides unmatched bunker-penetration capability.