Mind-boggling complexity: The challenge is to design an intelligent system that finds and destroys targets in a nuclear battlefield

The capabilities that the the defensive system of the Strategic Defense Initiative (SDI) will have to possess to be effective are discussed. The problems that arise in discriminating between warheads and decoys are treated. Attention is also given to the sensing technologies, including staring arrays, that will be required by the SDI system. The problems inherent in tracking a threat and managing a battle are also covered, together with the question whether the defensive systems should be under human control. Possible countermeasures that an enemy might use to neutralize the system are described.