The F-105, officially the Thunderchief but called the Thud by its crews, was designated as a fighter-bomber, used extensively in air operations against North Vietnam. The aircraft was really more of a light to medium bomber than a fighter, optimized for nuclear delivery. It was extremely fast and carried a heavy payload for its size, but neither had the agility for dogfighting nor a long-range air-to-air missile and thus did not do well in air superiority fighter roles.
It was extensively used in the Wild Weasel role, but had limited maneuverability if it needed to evade a surface-to-air missile. Eventually, it was replaced by different variants of the F-4 Phantom II, although the F-4G suppression of enemy air defense (SEAD) version was not used in Vietnam.