The classic problem of when to depend on lessons learned from previous conflicts and when to employ new tactics and technology always confronts military leaders. At the beginning of World War II, for example, Allied naval strategists were prepared to do battle using traditional tactics against surface vessels, but - this study contends - not against submarines; because the strategists failed to appreciate either the damage done by submarines in World War I or the tactics that had worked successfully against them. Consequently, from the beginning of World War II to mid-1943, German U-boats were able to mount a devastating campaign against Allied shipping. In Slide Rules and Submarines, Montgomery Meigs describes how the allies learned to counter the U-boat threat. Using new technology - and new tactics derived from scientific methods - they devised countermeasures to defeat the German submarine menace. Then, continuing to apply those successful measures, they went on to negate the Japanese submarine threat in the Pacific. The author cites the crucial role of civilian scientists - the "outsiders" - who worked with military staffs and operational commanders of the campaign at sea. Their open minds and objective methods were essential for the application of such tactical advances as sonar and radar, acoustic torpedoes, depth finders, and code breaking to the battle. As this study illustrates, the importance of such timely and innovative cooperation among scientists, the research and development community, and military commanders in bringing technological knowledge to bear for operational and strategic advantage cannot be overstated. Meigs? study of how such cooperation succeeded in the crucible of wartime crisis is itself an example of how the lessons of the past can serve us well today. J. A. Baldwin Vice Admiral, United States Navy President, National Defense University