The AGM-78 Standard ARM (Anti-Radiation Missile) was originally developed for the US Navy during the Vietnam War. General Dynamics was asked to create an air-launched ARM by modifying the RIM-66 SM-1 surface-to-air missile. This use of an off-the-shelf design greatly reduced development costs, and trials of the new weapon begun in 1967 after only a year of development. The first operational missiles were issued in early 1968.The first version of the missile, the A1 Mod 0, was little more than an air-launched RIM-66 with the Shrike anti-radar seeker head attached to the front. An Aerojet Mark 27 MOD 4 dual-thrust solid rocket powered the missile, which was fitted with a blast-fragmentation warhead. Although more capable, the AGM-78 was much more expensive than the AGM-45 and the Shrike continued in service for some time. The new missile was carried by the F-105F/G and the A-6B/E.Including all version, over 3,000 AGM-78 missiles were built. Production stopped in the after 1976, but the missile continued in service with the US Navy and US Air Force for almost a decade before the last examples were replaced by the AGM-88 HARM.