Bilateral treaty signed by the United States and the Soviet Union May 26, 1972; entered into force October 3, 1972. Both Parties agreed to limit qualitative improvement of their anti ballistic missile (ABM) technology and to have only two ABM deployment areas. Both nations later signed a Protocol to the Treaty, reducing the number of ABM deployment areas from two to one; the Protocol entered into force in 1976. The United States formally notified Russia December 13, 2001, of its decision to withdraw; this decision took effect June 13, 2002.