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Reviewed by:
  • Intelligence in War: Knowledge of the Enemy from Napoleon to Al-Qaeda, and: Uncovering Ways of War: U.S. Intelligence and Foreign Military Innovation, 1918–1941
  • Robert Angevine (bio)
Intelligence in War: Knowledge of the Enemy from Napoleon to Al-Qaeda. By John Keegan. New York: Alfred A. Knopf, 2003. Pp. xx+387. $30.
Uncovering Ways of War: U.S. Intelligence and Foreign Military Innovation, 1918–1941. By Thomas G. Mahnken. Ithaca, N.Y.: Cornell University Press, 2002. Pp. x+190. $35.

The importance of military intelligence has long been a matter of debate. More than two millenia ago, the Chinese general and military theorist Sun Tzu asserted that secret operations are essential in war, yet the term "military intelligence" is still often only half-jokingly described as an oxymoron. In these volumes, both John Keegan and Thomas Mahnken attempt to assess the value of intelligence to military organizations by examining historical case studies.

Despite the similarities in their general subject matter and methodology, the two authors reach strikingly different conclusions regarding the value of military intelligence. Keegan expresses a decidedly skeptical view of intelligence. After examining its role in Admiral Horatio Nelson's Nile campaign in 1798, General Thomas "Stonewall" Jackson's Shenandoah Valley campaign in 1862, cruiser warfare in World War I, the Allied defense of Crete in 1941, the Battle of Midway in 1942, the Battle of the Atlantic from 1939 to 1945, and the Allied attempts to counter the German V-weapons from 1942 to 1945, he concludes that intelligence, though perhaps necessary, is not sufficient for military victory.

Mahnken's judgment is more favorable. Based on his study of the ability of U.S. military intelligence organizations during the interwar period to recognize innovation in nine areas—Japanese carrier aviation, surface warfare, and amphibious warfare; German armored warfare, tactical aviation, and rocketry; and British tank experiments, armored warfare, and integrated air defense—he argues that intelligence agencies are able to detect foreign attempts to develop new ways of warfare and that intelligence can influence military technology and doctrine. Mahnken also suggests three factors that influence the capability of intelligence organizations to detect innovation. First, they are more likely to monitor the development of established weaponry than to search for new military systems. Second, they tend to pay more attention to technology and doctrine successfully demonstrated in combat than to those not proven in this way. Third, they find it easier to identify innovation in areas that their own services are exploring than in those the services have not examined or have rejected.

One explanation for the difference of opinion regarding the value of intelligence lies in the way the two authors define their subject. Keegan [End Page 881] intends the title of his book literally; he is interested only in wartime intelligence—the short-term, usually clandestine effort to collect information that contributes to success in battle. (He refers to peacetime intelligence as "espionage" and suggests that it is unseemly, untrustworthy, inscrutable, and worst of all, indecisive.) Keegan identifies two types of wartime intelligence, strategic intelligence and real-time intelligence. Strategic intelligence comprises general information on enemy strengths, weaknesses, intentions, and dispositions, while real-time intelligence is information on enemy location, composition, and objective acquired in time to make operational or tactical use of it.

Historically, the relative value of each type has been determined by the level of technological development, especially speed of communications. As long as this did not exceed the speed of enemy movement, strategic intelligence was most important, although it rarely conveyed an advantage in actual time and space. The introduction of more rapid means of communication beginning in the nineteenth century, however, made real-time intelligence possible. Keegan therefore sees the history of modern military intelligence as largely the history of signals intelligence. Yet he is careful to point out that even successful signals intelligence does not ensure military victory. The British ability to decrypt enciphered messages sent by the German Enigma machine provided foreknowledge of the timing, objectives, and composition of the airborne invasion of Crete in 1941, but could not prevent its loss.

Mahnken, in contrast to Keegan, focuses exclusively on peacetime intelligence, the long-term...

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