"While confident that our present strength will continue to deter a thermonuclear war, we must always be alert to the possibilities for limiting destruction which might be inflicted upon our people, cities and industry--should such a war be forced upon us. Many proposals have been advanced for means of limiting damage and destruction to the United States in the event of a thermonuclear war. Shifting strategy and advancing technology make the program of building adequate defenses against nuclear attack extremely complex. Decisions with respect to further limitation of damage require complex calculations concerning the effectiveness of many interrelated elements. Any comprehensive program would involve the expenditure of tens of billions of dollars. We must not shrink from any expense that is justified by its effectiveness, but we must not hastily expend vast sums on massive programs that do not meet this test. It is already clear that without fall-out shelter protection for our citizens, all defense weapons lose much of their effectiveness in saving lives. This also appears to be the least expensive way of saving millions of lives, and the one which has clear value even without other systems. We will continue our existing programs and start a program to increase the total inventory of shelters through a survey of private homes and other small structures. We shall continue the research and development which retains the options to deploy an anti-ballistic missile system, and manned interceptors and surface-to-air missiles against bombers."