Krav Maga ("contact combat") is a noncompetitive eclectic self-defense system developed in Israel that involves striking techniques, wrestling and grappling. Krav Maga is known for its focus on real-world situations and extremely efficient, brutal counter-attacks. It was derived from street-fighting skills developed by Imi Lichtenfeld, who made use of his training as a boxer and wrestler, as a means of defending the Jewish quarter against fascist groups in Bratislava in the mid-to-late 1930s. In the late-1940s, following his emigration to Israel, he began to provide lessons on combat training to what was to become the IDF, who went on to develop the system that became known as Krav Maga. It has since been refined for civilian, police and military applications.
Krav Maga has a philosophy emphasizing threat neutralization, simultaneous defensive and offensive maneuvers, and aggression. Krav Maga is used by Israeli Defense Forces, both regular and special forces, and several closely related variations have been developed and adopted by law enforcement and intelligence organizations, Mossad and Shin Bet. Outside Israel, Krav Maga is used by various special police, military and intelligence forces, such as American CIA, FBI, US Marshals, USAF, DEA, Sky Marshals, various police departments (SWAT teams), French GIGN, Belgian Army, etc. There are several organizations teaching variations of Krav Maga internationally.
Source: Wikipedia, "Krav Maga", available under the CC-BY-SA License.