It is America's largest non-nuclear bomb. Each can penetrate up to 60 meters beneath the surface to destroy its target.

One of the targets was Fordo, a uranium enrichment plant hidden in a remote mountainside that is vital to Iran's nuclear ambitions. We do not yet know the full scale of the damage at the facility. The US says it also hit two other nuclear sites - at Natanz and Isfahan.

The GBU-28 (Guided Bomb Unit‐28) is a 4,000–5,000-pound (1,800–2,300 kg) class laser-guided "bunker busting" bomb produced originally by the Watervliet Arsenal, Watervliet, New York.