A cruise missile defense system to protect the U.S. homeland would cost between $75 billion and $466 billion, a hefty sum that would protect the lower 48 states only and could still be defeated by an adversary capable of launching a cruise missile from near the U.S. border in Mexico or Canada as well as from the sea, near the U.S. coastline -- raising questions about the efficacy of any such investment. These are the key findings of a new...