Thud Ridge
Thud Ridge was the nickname given by United States Air Force F-105 Thunderchief pilots (the aircraft being nicknamed "Thud") during the Vietnam War to the Tam Dao range a 24 km, 5,000 feet (1,500 m) high ridge that ran parallel to the Red River approximately 32 km northwest of Hanoi, which was both a waypoint during air attacks and a terrain masking feature for ingressing fighters in the vicinity of Hanoi, North Vietnam. The North Vietnamese eventually installed anti-aircraft artillery on the ridge using heavy-lift helicopters.