This book brings together two important studies conducted by the Union of Concerned Scientists, one on anti-satellite weapons and the other on space-based missile defense. The conclusions of this group of experts are unambiguous and have already played an important role in the defense debate. Without a treaty soon forbidding testing, the authors foresee a destabilizing new arms race in space. As to a space-based missile defense, after a good deal of technical evaluation the report concludes that it would not be successful in halting incoming missiles-and in any case the Soviets could overcome it with additional ICBMs and more submarine-based cruise missiles. This is, of course, only one side of the debate, and a quickly shifting one at that, but it presents an argument which the proponents of the Administration's Strategic Defense Initiative have yet to successfully refute.