In the early 1950s, amid Cold War fears of a Soviet attack on Western Europe, brushfire conflicts, and bomber attacks on American cities, the U.S. Army began design studies in 1952 for a medium-range surface-to-air missile system. In July 1954, the Army awarded contracts to Raytheon Corporation for the missile and to Northrop Corporation for the launcher, radar, and fire-control system, and the missile was called HAWK, a name that only later acquired the backronym "Homing All-the-Way Killer" or, according to some sources, "Homing All-Weather Killer." The first HAWK test flight took place at White Sands Missile Range in August 1955, and testing increased rapidly, with 21 missiles fired there in 1956, 27 in 1957, 48 in 1958, and 83 in 1959. The system entered service with the Army in August 1959 and with the U.S. Marine Corps in 1960. Over a service life of more than 50 years, HAWK was used by more than two dozen nations, produced under license in Europe and Japan, and repeatedly upgraded to improve its ability to destroy low-altitude, high-speed aircraft, cruise missiles, and tactical ballistic missiles. Powered by an Aerojet General M22E8 solid-propellant rocket motor, the missile used an X-band radar seeker and depended on three radar units: the AN/MPQ-35 C-band Pulse Acquisition Radar for high- and medium-altitude threats, the AN/MPQ-34 Continuous Wave Acquisition Radar for low-altitude threats, and the AN/MPQ-33 High-Power Illumination radar to track and illuminate targets for semi-active homing. HAWK carried a 120-pound high-explosive blast-fragmentation warhead with impact and proximity fuzes, and although the Army considered fitting it with a sub-kiloton-yield W42 nuclear warhead in 1956, that effort was canceled at the end of 1960. HAWKs were carried on M192 triple-missile towed launchers, and more than 40,000 missiles of all versions were built, including foreign production. The U.S. Army deployed the system in Viet Nam and in the Persian Gulf, but American troops never fired it in combat. Its combat debut came in 1967, when Israel used it to destroy several Egyptian fighters in the Six-Day War, and Kuwaiti air defense units later used HAWKs during Iraq's invasion of Kuwait on August 2, 1990, bringing down 22 Iraqi aircraft and one helicopter.