High Quality Content by WIKIPEDIA articles! Ground Directed Bombing (GDB) is a type of attack mission performed by ground attack aircraft. Aircraft are remotely guided from the ground with the assistance of a height and direction-finding radar. In mature versions of the system, bomb release is controlled from the ground for precision. This enabled delivery of unguided bombs in poor weather and night, where pilots were unable to see the ground and identify targets. Until the introduction of GPS-guided bombs, this remained the primary method of bomb delivery in poor weather conditions. Over 75% of all bombs delivered in Vietnam, in particular all Operation Linebacker sorties, were performed with GDB.