The Missile Defense Agency loaded its fifth interceptor into an underground silo at Alaska’s Fort Greely this weekend. Earlier this year, the Pentagon said America’s new ABM system would become operational by Sept. 30, which is Thursday. Part of me wonders if the system didn’t become operational a few weeks ago, and the formal announcement is all that remains. Whatever the case, think about it: More than 21 years ago, Ronald Reagan called for the Strategic Defense Initiative; within two days, assuming the deadline holds, we’ll have a limited missile defense capable of protecting Americans from the likes of North Korea.