The AGM-12 Bullpup is an air-to-ground missile which was used on the A-4 Skyhawk, A-6 Intruder and F-4 Phantom among others. It has been superseded by more advanced armaments in American service. The Bullpup was the first mass-produced air-surface command guided missile, first deployed by the United States Navy in 1959 as the ASM-N-7 until it was redesignated AGM-12B in 1962. It was developed as a result of experiences in the Korean War where US airpower had great difficulty in destroying targets which required precise aiming and were often heavily defended, such as bridges.The Bullpup was roll-stabilized and visually guided by the pilot or weapons operator using a tracer on the back of the missile to track the weapon in flight while using a control joystick to steer it toward the target using radio signals. It was initially powered by a solid fuel rocket motor, and carried a 250 lb (110 kg) warhead. Later versions of the missile included upgrades such as a larger 1000 lb (450 kg) warhead, improved rocket motors, and improved guidance, and in one late version, the ability to carry a nuclear warhead.