Designed to replace the F-84, the Republic F-105 Thunderchief was unquestionably one of the finest fighter-bombers of all time and probably the most important tactical strike aircraft of the USAF during the Vietnam War. Designed by Alexander Kartveli and known affectionately as the "Thud", the F-105 was capable of deliviering up 6,700 different combinations of weapons (both conventional and nuclear) which included every US tactical missile and bomb during its time. It was also a large aircraft: the largest single-engined fighter ever used by the USAF but it could deliver a greater payload than a World War II-era heavy bomber, far more accurately, and doing it at supersonic speeds. The F-105 ultimately became Tactical Air Command's foremost strike aircraft during the 1960s, notably during the Rolling Thunder bombing campaign against North Vietnam: a total of over 380 F-105s were lost in combat, a testament to the intensity of their operations. Thunderchiefs were also used as Wild Weasel anti-radar operations but were slowly phased out in most roles by the F-4. There were no exports of this outstanding aircraft and were finally retired from reserve units in 1984.

The first YF-105A prototype had its maiden flight on 22 October 1955 and was ordered into production as the F-105B as well as the RF-105B photo-reconnaissance platform. Next up was the F-105D which featured new enignes, strengthened structures, a new search and ranging radar, and all-weather capability via an integrated fire control system. Later, the F-105F was intended as a combat capable trainer but many were converted to EF-105F Wild Weasel anti-radar platforms followed by the similar F-105G with new avionics.