The Mirage IV was designed in late 1950's a supersonic aircraft capable of carrying nuclear bombs and part of France nuclear triad. Although resembled the Mirage III, the IV was 50% longer, had double the wing surface and weapon load. Moreover, it had the same engine, twin SNECMA Atar side by side in the fuselage. First prototypes had the Atar 9C from the Mirage III and later the more powerful Atar 9K was used in production machines. Development was a challenge, since until 1959 when trials started, no other aircraft had been built capable of cruising at 1.8 Mach for long period of time. After some changes to the tail (enlarged with slight reduction in height, large increase in chord) and many test flights, the elegant french nuclear bomber was ready for production. the third prototype tested the refueling probe and the navigation system, while the second prototype did simulated bombings in Algeria desert in 1962-1963. Production lasted from 1964 to 1968, with only 62 airframes built. The Mirage IV was also capable of carrying convectional bombs or according to some sources up to four Martel anti-radiation missiles. But in that role the two large fuel tanks (2500 Lt each) could not be used. Total fuel capacity internal was 14,000 Lt plus 5000 Lt external, giving combat radius 1240km (670nm) with half duration of flight at supersonic speed. This range was not enough, so Armée de l'Air purchased 12(+2 for spares) Boeing KC-135F for air tankers.
Until 1971 the Mirage IV was the sole means of delivering nuclear ordnance, one AN-11 or one AN-22 free fall nuclear bomb under belly.