The word "supergroup" has often been used to describe O.S.I., one of the best-known progressive metal/progressive rock acts to emerge in the United States in the 2000s -- and considering who has been leading O.S.I., that word is not an exaggeration. The leaders of O.S.I. have included guitarist/keyboardist Jim Matheos and lead singer/keyboardist Kevin Moore, both of whom bring strong prog and metal credentials to the table. Moore is a former member of Dream Theater (one of the top progressive metal bands of the 1990s and 2000s) and the founder of Chroma Key (whose work is prog rock but not prog metal), while Matheos' résumé includes his many years as guitarist for the well-known metal band Fates Warning. Other participants in O.S.I. have included drummer Mike Portnoy (known for his association with Dream Theater) and bassist Sean Malone of Gordian Knot (an instrumental progressive metal/progressive rock group that has been influenced by jazz-rock fusion).

O.S.I.'s participants have varied from one album to the next, but Matheos and Moore have been the core of the group -- which has been heavily influenced by alternative rock and alternative metal. Some progressive metal bands have been oblivious to the alternative metal and alternative rock of the 1990s and 2000s; all of their prog and metal influences come from the 1960s, 1970s, and 1980s, and they operate with a decidedly pre-Nevermind outlook (Nevermind was the seminal 1991 blockbuster that turned Nirvana into alternative rock superstars and did a great deal to make alternative rock mainstream). But instead of ignoring alternative rock and alternative metal, O.S.I. have opted to draw on influences from different eras. O.S.I.'s long list of influences has included, among others, Pink Floyd, Yes, and King Crimson as well as Radiohead and Nirvana -- and some of Moore's admirers have been surprised to find out that O.S.I. don't sound a lot like Dream Theater. But in fact, Dream Theater have not been a major influence on O.S.I.'s work.

Formed in 2003, O.S.I. named themselves after the Office of Strategic Influence -- a short-lived, controversial government agency that the United States Department of Defense established in late October 2001 in response to the terrorist attacks of 9/11. According to BBC News and other major news agencies, the purpose of the Office of Strategic Influence was to spread pro-George W. Bush Administration propaganda and disinformation in foreign countries, but in 2002, Donald H. Rumsfeld (who served as secretary of defense under President George W. Bush until his resignation in late 2006) was quoted as saying that the Office of Strategic Influence had been discontinued in name even though its activities continued. By the time the progressive metal/progressive rock supergroup O.S.I. were formed in 2003, the Office of Strategic Influence no longer existed as an official department. O.S.I.'s first album, Office of Strategic Influence, was released by Inside Out/SPV in 2003; that debut was followed by O.S.I.'s subsequent Inside Out/SPV releases Free (which was their second album) in 2006 and Blood (their third album) in 2009. ~ Alex Henderson, Rovi