The ABM Treaty and U.S. Missile Defense Program Wu Zhan(7) The article is a summary of the history of U.S. missile defense in the past fifty years. Owing to the extreme difficulties in the technologies, the United States and the Soviet Union signed the ABM Treaty and stopped the deployment in 1972, but the research and development continued. The United States played an important role in the technological race in the decades afterwards, doing a lot of fruitless work. The later disintegration of the Soviet Union gave rise to Russia and some independent republics which are no longer major threats to the United States. Meanwhile, Third World countries began to develop ballistic missiles, constituting new threats even though backward in technological terms. The United States has given notice to Russia in withdrawing from the treaty and will make use of its experience in ABM development to defend itself against missile attacks from the Third World countries.