Founded by Jim Dunnigan in 1969, SPI was a publisher of board wargames during the 1970s and early 1980s, when it went bankrupt. SPI also published several magazines, including Strategy & Tactics, Moves and Ares.
Several SPI titles have been republished by Decision Games (I), who are also the current publishers of Strategy & Tactics magazine.
Some of them SPI titles were published in Poland in the late 80's and early 90's by the Encore, but without license.
Source: Wikipedia, summary of "Simulations_Publications" article, available under the CC-BY-SA License.