Sept. 8, 1944: The missile age begins when the first German V-2 rocket hits London. After the war, Allies discover Nazi plans to build an intercontinental ballistic missile to hit New York.

March 14, 1969: President Nixon decides to develop nuclear-tipped interceptors to protect the nation's nuclear arsenal from Soviet attack.

May 26, 1972: Nixon and Soviet General Secretary Leonid Brezhnev sign the Anti-Ballistic Missile Treaty, which limits the number of missile-defense sites each nation can have.

Oct. 2, 1975: House of Representatives votes to kill Nixon's missile-defense system, called Safeguard, a day after it was declared operational.

The Senate later followed suit. Lawmakers cite its limited usefulness in the event of a full-scale Soviet attack. Then-Defense Secretary Donald Rumsfeld shuts down the system.

March 23, 1983: President Reagan announces a major effort to determine the feasibility of a new missile-defense system,

dubbed Star Wars.

June 10, 1984: First successful test of "hit-to-kill" technology, as a "kill vehicle" destroys a dummy warhead.

Sept. 1, 2000: President Clinton decides not to move the national missile-defense program beyond the research phase. He cites poor test results and inconsistency with the nation's foreign policy.

Dec. 13, 2001: President Bush notifies the Russian government that the U.S. is withdrawing from the Anti-Ballistic Missile Treaty, signaling his intent to deploy the missile-defense system.

July 22, 2004: Workers place the first interceptor in an underground silo at Fort Greely in Alaska.

Sources: Missile Defense Agency and Union of Concerned Scientists