The Collective Security Treaty Organization is an intergovernmental military alliance, acting as counterpart to the NATO alliance, which was signed on 15 May 1992. In 1992, six post-Soviet states belonging to the Commonwealth of Independent States—Russia, Armenia, Kazakhstan, Kyrgyzstan, Tajikistan, and Uzbekistan—signed the Collective Security Treaty (also referred to as the "Tashkent Pact" or "Tashkent Treaty"). Three other post-Soviet states—Azerbaijan, Belarus, and Georgia—signed the next year and the treaty took effect in 1994. Five years later, six of the nine—all but Azerbaijan, Georgia, and Uzbekistan—agreed to renew the treaty for five more years, and in 2002 those six agreed to create the Collective Security Treaty Organization as a military alliance. Uzbekistan rejoined the CSTO in 2006 but withdrew in 2012.
The CSTO is an observer organization at the United Nations General Assembly.
The CSTO employs a "rotating presidency" system in which the country leading the CSTO alternates every year.