STEVEN PIFER – On March 23, 1983, Ronald Reagan announced the Strategic Defense Initiative, popularly known as “Star Wars.†After thirty-two years and tens of billions of dollars, defending the U.S. homeland against attack by strategic ballistic missiles still poses a daunting challenge. Missile defense ambitions have been regularly scaled-back. The United States should make prudent investments in missile defense as part of its overall force mix. But Washington should bear in mind the limits of technology and the nature of the relationship between offense and defense, in which offense has and, for the foreseeable future will retain, the advantage.