The Patriot air defense missile system was designed by Raytheon and first fielded in 1984. Four years later, a missile defense capability was added, mainly through changes to the guidance software. In the 1991 Gulf War, the system had mixed success against Iraqi short-range Scud missiles, and it became clear that its blast-fragmentation warhead was inadequate to the task. Lockheed Martin then leveraged its previous work on hit-to-kill technology to develop the PAC-3 missile for Patriot batteries. The combination of an agile airframe with a millimeter-wave seeker and very fast computing of the hit-to-algorithms, together with an upgraded acquisition radar on the ground, proved successful. Four years after it first flew, the PAC-3 missile scored operational success by destroying two Iraqi ballistic missiles during the second Gulf War in 2003.
In addition to the U.S., 12 nations have bought the Patriot system. In Europe, Germany and the Netherlands have PAC-3s, while Greece and Spain operate the less capable PAC-2.