For the past week, a controversy has raged over whether or not the Bush administration neglected vital warnings prior to the terrorist attacks on September 11. Two intelligence reports, an FBI memo in July pointing to the danger of Arab pilots receiving flight training in the United States, and a CIA briefing in August warning the president of the possibility that Osama Bin-Laden would try to hijack an American airliner, are at the center of the storm. Members of Congress and the media have charged that President Bush and his advisers failed to connect the dots, to use the current cliché, which would have enabled them to foil the 9-11 plot.

A similar controversy developed a half-century ago over the intelligence failure at Pearl Harbor. Just as with 9-11, the American people immediately closed ranks behind the president, in this case Franklin D. Roosevelt, who quickly persuaded Congress to declare war against Japan. Soon after, however, dissenting voices began to ask why the United States had been caught by surprise. In the election-year l944 , the debate became partisan as Republicans began to insinuate that FDR had deliberately exposed the American fleet to attack in order to enter the Second World War. During the campaign, vice presidential candidate John W. Bricker accused the President of withholding facts about"the disgraceful Pearl Harbor episode," while Representative Clare Booth Luce claimed that President Roosevelt"lied us into a war because he did not have the courage to lead us into it," calling Pearl Harbor,"Mr. Roosevelt's shame." ¹ Only after General George Marshall wrote privately to GOP candidate Thomas Dewey, warning that the Pearl Harbor controversy risked disclosing to the Japanese that the U.S. had broken their secret codes, did the Republicans abandon this issue.

After the war was over, a Joint Committee of Congress held extensive hearings in late 1945 and early 1946 that failed to reach consensus. The Democratic majority, while retreating from the wartime tactic of placing all the blame on General Walter Short and Admiral Husband Kimmel, the Army and Navy commanders in Hawaii, still exonerated the administration, while the Republican minority argued that responsibility extended all the way up the chain of command to the White House, but refrained from accusing FDR of deliberately arranging for the attack. Subsequently, revisionist historians such as Charles Tansill pursued the"back door to war" thesis, while the majority of scholars tended to agree with Gordon Prange, whose exhaustive book put the primary responsibility for Pearl Harbor on the Japanese.

Another historian, Roberta Wohlstetter, provided the most convincing explanation for the intelligence failure at Pearl Harbor in her l962 book, Pearl Harbor: Warning and Decision. The wife of nuclear theorist Albert Wohlstetter of RAND, she shared her husband's concern over American nuclear vulnerability to a Soviet first strike in the nuclear age. Her book was thus an attempt to use the example of Pearl Harbor to assess the likelihood of a successful nuclear surprise attack on the United States.

Relying on the 39 volumes of the l945-46 congressional hearings, as well as the extensive secondary literature, Wohlstetter set out to explain what had gone wrong in l94l. The primary difficulty, she argued, was separating"signals" (intelligence data that pointed to what actually happened) from"noise" (the flood of conflicting reports and assessments that pointed toward other possible outcomes)."To understand the fact of surprise," she wrote,"it is necessary to examine the characteristics of the noise as well as the signals that after the event are clearly seen to herald the attack." (p. 3)

Wohlstetter explored the range of contingencies facing American intelligence analysts in the months prior to the Pearl Harbor attack in l94l. Several times warnings were sent to Pacific commanders referring to the likelihood of a Japanese move to the north - an invasion of the Pacific maritime provinces of the Soviet Union. Other warnings dealt with the oil-rich Dutch East Indies, the Philippines, and most often, the Panama Canal, vital to American defense in the Pacific. As it turned out, the Japanese did attack the Dutch East Indies and the Philippines, as well as Hawaii, but not Siberia or Panama. But only after the attack on Pearl Harbor did the signals become clear -- only then could an investigator focus on the data pointing to the likelihood of an attack on the American fleet and dismiss information suggesting moves against the Panama Canal as"noise."

Roberta Wohlstetter's conclusions about the Pearl Harbor attack bear directly on the question of an intelligence failure on September 11, 2001. She points out the folly of 20-20 hindsight by observing that"it is much easier after the event to sort out the relevant from the irrelevant signals.""After the event," she continues,"of course, a signal is always crystal clear; we can now see what disaster it was signaling, since the disaster has occurred." (p. 387) In the case of Pearl Harbor, she contends,"there was a good deal of evidence available to support all the wrong interpretations of last-minute signals, and the interpretations appeared wrong only after the event." (p. 392)

Even more significant than her analysis of Pearl Harbor is Wohlstetter's conclusion regarding future contingencies. Concerned about the risk of a surprise nuclear attack at the height of the Cold War, she concludes that there is no sure way to anticipate and prevent such a calamity. The greatest danger, she warns, is the tendency of people"to predict that events they want to happen actually will happen." (p. 397) and to ignore the unthinkable or the highly improbable. In his introduction to her book, nuclear strategist Thomas C. Schelling reinforces this point:"There is a tendency in our planning to confuse the unfamiliar with the improbable. The contingency we have not considered seriously looks strange; what looks strange is thought improbable; what is improbable need not be considered seriously." (p. vii)

Wohlstetter's realistic advice, that we must learn to live with uncertainty, is as true for the continuing threat of terrorist attacks on the American homeland today as it was for the danger of a nuclear Pearl Harbor in the Cold War era. Unpleasant as it is, we have to put up with a high degree of uncertainty, suffer under vague warnings of impending terrorist acts and frequent false alarms, because we must"accept the fact that the signal picture for impending attacks is almost sure to be ambiguous." (p. 401)

Those who today are genuinely concerned about how to use intelligence data to prevent future terrorist attacks should consult Roberta Wohlstetter's enduring book. The events of 9-11 proved what Thomas Schelling argued with so much foresight in its preface:

The danger is not that we shall read the signals and indicators with too little skill; the danger is in a poverty of expectations -- a routine obsession with a few dangers that may be familiar rather than likely."

The attacks on the Pentagon and the World Trade Center make these words as relevant in 2002 as they were when written four decades ago.

¹ Martin Melosi, The Shadow of Pearl Harbor (l977), p. 81; Robert A. Divine, Foreign Policy and Presidential Elections, l940-l948 (1974), p. 146.