The deployment was designed to initially supplement and then replace gun batteries deployed around the nation's major urban areas and vital military installations. The defense areas consisted of major cities and selected United States Air Force Strategic Air Command bases which were deemed vital to national defense. The original basing strategy projected a central missile assembly point from which missiles would be taken out to prepared above-ground launch racks ringing the defended area. However, the Army discarded this semimobile concept because the system needed to be ready for instantaneous action to fend off a "surprise attack." Instead, a fixed-site scheme was devised.