Former President Ronald Reagan’s 1983 speech addressed the vision of a world capable of defending itself against a nuclear attack rather than having its defense based solely on the threat of mutual destruction. The Strategic Defensive Initiative Organization (SDIO) has been dedicated to this goal, with the U.S. Army Strategic Defense Command (SDC) as its largest player. Over 30 years of Army research and technology development provides valuable contributions to all five SDIO program elements. These areas include: Surveillance, Acquisition, Tracking, and Kill Assessment; Kinetic Energy Weapons; Direct Energy Weapons; Survivability, Lethality, and Key Technologies; Systems Analysis and Battle Management. SDC research includes boost, postboost, and midcourse tiers, as well as the terminal defensive tier where the Army has always been preeminent. Programs and experiments focus on interceptors, sensors, communications, and laser development. Additionally, the Army plays a key role in Theater Missile Defense. Dedicated research has yielded many important scientific breakthroughs and successful technology demonstrations. Building on its past contributions, the Army continues to respond to the complex, challenging demand for strategic defense. © ASCE.