1958: President Eisenhower approves Nike-Zeus anti-missile defense. The program dies for lack of funding.
1969: President Nixon announces Safeguard anti-missile system, later scrapped.
1972: Nixon signs ABM Treaty, banning all but limited U.S. and Russian anti-missile systems. The countries also sign SALT I, freezing levels of offensive missiles.
1979: President Carter signs SALT II with Soviets, limiting offensive missiles to 2,400 on each side. Treaty is never ratified.
1983: President Reagan announces Strategic Defense Initiative, or "star wars," space-based anti-missile system.
1991: President Bush signs START I treaty with Soviets, cutting both sides to 1,600 offensive missiles.
1993: Bush signs START II treaty with Russia, reducing warheads on both sides by two-thirds, to about 3,000.
1998: Rumsfeld Commission emphasizes nuclear threats from Third World nations.
1999: President Clinton announces U.S. intention to seek ABM treaty revisions and signs bill making missile defense official policy.
2000: Russian parliament approves START II. Clinton visits Moscow seeking Russian approval for ABM treaty modifications.