From this perspective, the call for a layered defense makes a lot of sense.

CENTERFORSECURITYPOLICY: 33 Minutes

In other words, a fully funded layered defense could have four or five chances to stop a missile.

CENTERFORSECURITYPOLICY: 33 Minutes

The reason they call it a "family system" or a "layered defense" is that the tracking and targeting systems of each layer of technology enhance each others accuracy.

CENTERFORSECURITYPOLICY: 33 Minutes

This "layered" defense greatly increases the probability of protecting large areas against missile strikes.

CENTERFORSECURITYPOLICY: Get On With It: Time To Deploy Sea-Based Missile Defenses

The system on its way to the island is part of a "layered" defense giving the military multiple opportunities to shoot down incoming missiles and warheads before they reach their targets.

NPR: North Korea Threats Spark Buzz On Guam, Not Panic

Ronald Kadish (USAF), said the United States would need a layered type of defense across a broad front to address an evolving missile threat.

CENTERFORSECURITYPOLICY: Let Chiefs Lead on Missile Defense

Interestingly, Mr. Davis has cited the importance of layered or "tiered" defense among his rationales for restarting the canceled E2I secondary interceptor for the single ground-based defense site he advocates -- despite the fact that the E2I system does not represent an independent layer.

CENTERFORSECURITYPOLICY: Center For Security Policy