First conceived in 1955 as a nuclear bomber, the fighter-bomber F-105 Thunderchief was the largest, heaviest, and loudest warplane of its era which earned its glory from fighting in Vietnam. Of the 830 total production, about 50% (397) were lost in action in fierce attacks against heavily defended N Vietnamese HVTs (High-Value Targets). The name "Thud" came about by the sound they made when they crashed, but they penalized the NVA heavily for any losses and even shot down MiG-17s by the dozens. This aircraft was the main weapon of "Operation Rolling Thunder" from 1965-68. Powered by a single P&W J75 of 26,000 lb st with afterburner the Thud could hit Mach 2.1 at 33,000 ft. It carried 7 tons of ordnance and also could mount AIM-9s for ATA. It also carried a Vulcan cannon for defense. The Thud's greatest target was Hanoi, which at the time was the most heavily defended city on earth with thousands of radar-guided missiles and radar-slaved AA guns in addition to MiGs in the air. The Thuds would drink from a tanker first for max. fuel load to feed the afterburners, approach low hidden by terrain, and then pop up and drop all of their ordnance on bridges, airfields, arms and supply depots, and NVA barracks. After the B-52, the F-105 was the greatest threat to N Vietnam.