Vladimir Putin believes that he can send his army into Ukraine to commit mass murder on a scale not seen since Hitler’s Germany because he is secure in the knowledge that the civilized world is limited in what it can do to stop him. If NATO were to send troops into Ukraine to save its people from the wrath of the Russian army, Putin darkly hints that nuclear weapons would be unleashed. Just as during the Cold War, such an act would be the end of human civilization.

Isn’t it too bad that a way doesn’t exist to stop a nuclear exchange with “the means of rendering these nuclear weapons impotent and obsolete?” The question was first posed 40 years ago by President Ronald Reagan when he proposed the Strategic Defense Initiative as a way to break the balance of terror and lift the prospect of a global thermonuclear holocaust. Reagan and his advisers envisioned a multilayered defense system, much of it space-based, that would stop a nuclear attack by shooting down missiles before they reached their targets.