The Japanese Defense Agency (JDA) selected PATRIOT as a successor to NIKE-J in August, 1984.
Raytheon Company and Mitsubishi Heavy Industries (MHI), the prime contractor in Japan, initiated a licensed co–production program, in October 1985.
In addition to MHI, there are many sub-contractors who manufacture a portion of the Patriot System.
Product Improvements (PI) have been incorporated within the Patriot System between Raytheon and MHI via direct commercial sale contracts.
The PI program was fielded in Japan in January 1996, PI-2 in September 2001 and the most recent ongoing upgrade, PI-2+, fielded in July 2003. The Upgrade to PI-3 (Configuration 3) is in process.
