In this chapter we consider problems where multiple attackers are approaching a target, hoping to kill it by overwhelming its defenses. The defense is armed with some anti-attacker weapons called interceptors , each of which can kill only the attacker to which it is assigned. The goal is to use the interceptors to maximize the survival probability of the target. Instead of assigning weapons to nondescript targets, as in Chapters 2 and 3, the defense now assigns them to attackers. The “targets” are now the things being defended.