USA TODAY: U.S. missile defense plans for zapping North Korean missiles.

“Missile defense buys you time and opens windows,” said Todd Harrison, director of the Aerospace Security Project at the Center for Security and International Studies. “The way you protect yourself from a missile attack is through deterrence. You show your adversary that you can hold them off and strike back at them.”

Demonstrating anti-missile capabilities is one component of Trump’s Option 4. Strike back is Option 6.