For the uninitiated, the series centers around the Mithril mercenary group on a parallel Earth in which the Cold War didn't end in 1991. The novel inspired three anime shows, namely: Full Metal Panic! (2002), Full Metal Panic? Fumoffu (2003), and Full Metal Panic! The Second Raid (2005). It also inspired an OVA back in 2006.
[Source: Anime News Network]