It was technological innovation that broke America from the orbit of the doctrine of nuclear mutual assured destruction, known as MAD. Three decades ago, the world’s two great superpowers were holding each other’s large population centers hostage.

President Reagan changed all this with a nationally televised speech 30 years ago this month, in which he announced the United States would pursue defensive countermeasures that could render ballistic missiles “impotent and obsolete.” The speech came just a few weeks after he had described the Soviet Union as an “evil empire.”