The former Soviet Union's military intelligence bureau, and the current Intelligence DIrectorate of the General Staff of the Armed Forces of the Russian Federation.
The GRU is an intelligence agency that has existed since the Soviet era. While the former KGB was subordinate to the Council of Ministers -- making it a secret police organization -- the GRU lay under the jurisdiction of the military. It was said that even the leader of the Soviet Union (the General Secretary) had no direct line of communication with the organization. Its main activities include espionage, misinformation, destruction of military targets, and subversive operations behind enemy lines. It is rumored that during the Cold War, GRU operatives posed as Olympic athletes in order to infiltrate NATO nations. Many commando units are part of the GRU, such as the famed Spetsnaz, the Russian Airborne Troops, and OMON (the Russian Ministry of Internal Affairs' military anti-terrorist division).