The Dassault Mirage IV was a French supersonic strategic bomber and deep-reconnaissance aircraft. Developed by Dassault Aviation, the aircraft entered service with the French Air Force in October 1964. For many years it was a vital part of the nuclear triad of the Force de Frappe, France's nuclear deterrent striking force. The Mirage IV was retired from the nuclear strike role in 1996, and the type was entirely retired from operational service in 2005. During the 1960s, there were plans to export the Mirage IV. In one proposal, Dassault would have entered a partnership with the British Aircraft Corporation to jointly produce a Mirage IV variant for the Royal Air Force and potentially for other export customers, but this project did not come to fruition. The Mirage IV was ultimately not adopted by any other operators. Development Origins During the 1950s, France embarked on an extensive military program to produce nuclear weapons; however, it was acknowledged that existing French aircraft were unsuitable for the task of delivering the weapons. Thus, the development of a supersonic bomber designed to carry out the delivery mission started in 1956 as a part of the wider development of France's independent nuclear deterrent. In May 1956, the Guy Mollet government drew up a specification for an aerially-refuelable supersonic bomber capable of carrying a 3-metric-ton, 5.2-metre-long nuclear bomb 2,000 km (without aerial refuelling). According to aviation authors Bill Gunston and Peter Gilchrist, the specification's inclusion of supersonic speed was "surprising" to many at the time. The final specifications, jointly defined by government authorities and Dassault staff, were approved on 20 March 1957. Sud Aviation and Nord Aviation both submitted competing proposals, both based on existing aircraft; Sud Aviation proposed the Super Vautour, a stretched Sud Aviation Vautour with thrust SNECMA Atar engines and a combat radius of at Mach 0.9. Dassault's proposal for what became the Mirage IV was chosen on the basis of lower cost and anticipated simpler development, being based upon a proposed early 1956 twin-engined night-fighter derived from the Dassault Mirage III fighter and the unbuilt Mirage II interceptor. In April 1957, Dassault were informed that they had won the design competition. Dassault's resulting prototype, dubbed Mirage IV 01, looked a lot like the Mirage IIIA, even though it had double the wing surface, two engines instead of one, and twice the unladen weight. The Mirage IV also carried three times more internal