The chairman of the KGB was the head of the Committee for State Security (KGB), the main security agency of the Soviet Union in 1954–1991. He was assisted by one or two first deputy chairmen, and four to six deputy chairmen. He was also the head of the Collegium of the KGB—which consisted of the chairman, deputy chairmen, directorate chiefs, and one or two republic-level KGB organization chairmen—who affected key policy decisions.