"Missile defense is NP-complete."
The Weapon-Target Assignment (WTA) problem:
Given interceptors, targets, a value for each target, a probability matrix for the probability the interceptor destroys the target, the objective is to maximize the total expected value of successfully defended assets, subject to each interceptor being assigned to at most one warhead.
https://smu160.github.io/posts/missile-defense-is-np-complete/