The USAF Republic F-105 Thunderchief or "Thud" was made famous for the part it played in the Vietnam War delivering conventional weapons even though it was designed as a nuclear strike supersonic tactical fighter bomber for a potential European Cold War conflict with the Soviet Union. It was designed for high-speed low-altitude penetration strikes carrying a single nuclear weapon internally.

It could reach Mach 2. It was a mid-wing monoplane with a 45 degrees swept wing and tail surfaces. The nose housed the multi-mode radar. At the time it was the largest single seat fighter ever built. It's size enabled more fuel and ammunition for its 20 mm rotary nose cannon to be carried along with bombs or a single nuclear weapon. It could carry other air-to-ground munitions, such as napalm canisters and 70 millimeter (2.75 inch) unguided rocket pods. It could also carry four AIM-9 Sidewinder AAMs, with a special rack allowing two to be carried on a single stores pylon.

The Republic F-105 Thunderchief could carry up to five tons of bombs. It did most of the USAF's bombing missions in the Vietnam war. It normally carried a cargo of eight 750-pound bombs. Though primarily a ground attack aircraft it could defend itself and engage in air to air dog fights. The F105 is credited with shooting down several MiG-17s and MiG-21s over Vietnam.

The USAF awarded the Republic Corporation a contract to build the F105 in 1952. It first flew on 26th May 1956 and entered service in January 1959 and was finally retired after over 800 were produced in 1984. The Republic F-105 Thunderchief was replaced by the F-4 Phantom II in its strike role. The F-105 could take a lot of punishment and come back home. It was generally liked by the pilots. The major complaint against the F-105 was that it needed a long runway to get into the air. It was not very maneuverable but it could fly very fast at low altitude.

Flak and surface to air missiles SAMs were the greatest hazard to F105s. 312 Thunderchiefs were shot down by this ground fire compaired with 22 F105s claimed as having been shot down by North Vietnamese MiGs. The F-105 Republic Thunderchief is credited with 27.5 MiG Kills. 24.5 of these kills were by cannon which contrasts with the kill records of the Vought F-8 Crusader and the F-4 Phantom, in which most kills were achieved with missiles.

A two-seat Wild Weasel version was later developed for use in the specialized Suppression of Enemy Air Defenses (SEAD) role against surface-to-air missile sites. This was a dangerous missions which often required the Republic F-105 Thunderchief Wild Weasel varient to be the "first in, last out", suppressing enemy air defenses and keeping them suppressed while strike aircraft accomplished their missions and then left the area. the "Wild Weasel" variants of the F-105 remained in service until 1984, when they were replaced by a specialized F-4G "Wild Weasel V".

The standard Republic F-105 Thunderchief was replaced as a strike aircraft over North Vietnam by both the McDonnell Douglas F-4 Phantom II and the swing-wing General Dynamics F-111 Aardvark. Of the 833 F-105s built, nearly 50% were lost in Vietnam.