Author & Context

Roberta Wohlstetter, (August 22, 1912- January 6, 2007), was one of America's most important historians of military intelligence. Her most influential work is Pearl Harbor: Warning and Decision. The former secretary of defense, Donald Rumsfeld, is said to have required that his aides read it. Indeed, it was brought during discussions of intelligence failures leading to the successful al-Qaeda attack on the World Trade Center and Pentagon.


This classic study of military intelligence attempts to explain the causes of the U.S. intelligence failures that led to Imperial Japan's 1941 surprise attack. In the years preceding the attack, U.S. code breakers were routinely reading much of the Japanese military and diplomatic traffic. However, a Japanese attack came as both a strategic and tactical surprise. On the strategic level, U.S. intelligence analysts viewed the attack as unlikely because Japan could not expect to win the subsequent war (as it happens, Japanese planners had never completed a thorough strategic assessment. They were unwilling to abandon their expansion in east Asia and viewed the attack as the best way to start the inevitable confrontation). Furthermore, on several occasions during 1940-41 U.S. forces were put on high alert but no attack came, leading to fatigue. Finally, it was believed that the logical place for a Japanese attack would be in the Philippines. The book argues, in part, that intelligence failures are to be expected because of the difficulty identifying "signals" from the background "noise" of raw facts, regardless of the quantity of the latter.

On a tactical level, the attack came as a surprise because warning mechanisms - radar stations and patrol planes - were not deployed, although senior officers came to believe that they were.


  • Even with signals, the leap of inference is the hard part
  • Not lack of info, rather a a misuse/misperception and failure to see the big picture
  • Bickering between Air Corps and Signal Corps over radar (Model 2/Model 3)
  • Time for information to relay…both tactically and strategically
  • USN and USA intel commanders on Hawaii did not have a good relationship
  • Lack of collaboration
  • War warning memo assumed attack in Philippines, put peoples minds and focus there.
  • Radio silence prevents reporting of strange ship
  • Belief that 10 minutes warning would always be available
  • Belief that the fleet presence would deter Japan and failure to remove it because it would look like appeasement
  • Unprotected COG based on misunderstanding the enemy
  • Army’s failure to see links between economic and diplomatic events
  • Churchill belief that America would not be attacked until after Russia
  • Lots of information: how to package and communicate it from Washington to theater
  • Turner believed Kimmel and Short were in lockstep and that press coverage was good in Honolulu…not so
  • Inference/analysis will always be hazardous and noise-filled
  • Washington had all the info, but the theaters had the expertise. The link between them was impractical. Everyone believed the Pac Fleet was a deterrent rather than a vulnerability
  • Should have prepared for most dangerous (Attack at PH), any other attack/area would have ensured the fleet was still available.
  • MOD II and III are prevalent. The systemic filters and behavior forces the perception and action towards what happened.
  • C2 issues, personnel issues between army, navy and gen officers. Totally not a good situation but still with the best system/personnel in place there might still be a PH attack.

Applications to Strategy

  • Signals and Noise. There are structural, organizational, and individual contributors to the failure to arrest surprise. Examine organizations, leaders, and collective mentality (paradigm) for tendencies that can allow signals to go unnoticed
  • Expect the Unexpected. Strategists should always have plans to address the most likely branches, but should at least consider the most significant but less likely; occasionally evaluate the strategy using the question: “what is the unthinkable surprise that could defeat this strategy?”
  • Uncertainty. Strive to minimize it while acknowledging its ubiquity.

Links with other Books/Concepts

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