1983: President Ronald Reagan announces plans for an extensive program to examine the feasibility of a missile defense program. The concept—derided as "Star Wars" by opponents in Congress—revises the nation's 35-year-old nuclear strategy by focusing on missile defense rather than the ability to retaliate against nuclear attack.

2001: Although Russia, China, and North Korea tell the U.N. Disarmament Commission that a U.S. missile defense system would threaten international security, trigger a new arms race, and undermine the Anti-Ballistic Missile Treaty, President Bush advocates further developing the system. The proposed 2002 defense budget allots $8.3 billion for missile defense.

1986: Washington severs all economic and commercial relations with Libya, accusing it of giving aid to international terrorists.

2001: Following the Libyan handover of two suspects in the 1988 bombing of Pan Am flight 103 to stand trial before a Scottish Court in the Netherlands, the United States modifies its...