Mrs. Wohlstetter, a historian of military intelligence, explained in her 1962 book "Pearl Harbor: Warning and Decision'' how analysts failed to sort the important signals about an impending attack from the overwhelming noise of irrelevant information. Although intelligence analysts had broken the Japanese diplomatic code, that information was so highly classified and jealously guarded that it was never shared with those who could have acted on the information.

Her meticulous research led her to conclude that the failure to foresee the attack came "not for want of the relevant materials, but because of a plethora of irrelevant ones."

The Sept. 11 Commission cited her work in its report on the failures of national security in 2001.

She and her husband, Albert Wohlstetter, a nuclear deterrence analyst, received the Presidential Medal of Freedom from President Ronald Reagan in 1985.

"[They] have shaped the ideas and deeds of statesmen and have helped create a safer world. Over four decades, they have marshaled logic, science and history and enlarged our democracy's capacity to learn and to act," Reagan said at the time.

"Roberta and Albert Wohlstetter are to national security what Will and Ariel Durant were to history," said Henry D. Sokolski, executive director of the Nonproliferation Policy Education Center, where Mrs.

Wohlstetter served on the board. "She was the go-to, both for Albert and for anyone seeking sound counsel."

But Mrs. Wohlstetter's primary work almost didn't get published.

As a government consultant with a security clearance, she was required to submit her work to the Pentagon for prepublication review. Because all of her sources were unclassified, and most came directly from congressional testimony, she didn't expect trouble.

The Defense Department sent it to the National Security Agency, "where they classify everything," she told Washington Post reporter George Lardner Jr. in 1990. At the NSA, the agency that eavesdrops on the world, "whenever they see the word 'code,' that sets up alarms. If something is written about codes, they get uptight."

The NSA not only ordered the book classified but demanded that all copies of the manuscript be destroyed. When Mrs. Wohlstetter offered to delete any offending material, she was told that she did not hold the proper clearances to read her book.

Publication was suppressed for five years, until the Kennedy administration took office and new Pentagon officials lifted the ban. The book, which had been set in type before it was censored, was published without a word being changed, Mrs. Wohlstetter said.

Her book was awarded the Bancroft Prize in history in 1962, and she was named the Los Angeles Times woman of the year in 1963. She taught at the University of Chicago, Howard University and Barnard College. She was on the staff at RAND, the California think tank, from 1948 until 1965 and remained its consultant until 2002.

She continued to work in the male-dominated fields of political-military history and foreign policy, particularly in the use of intelligence in crisis decision-making.

In 1975, after India surprised the world by detonating a nuclear device, Mrs. Wohlstetter, with her husband and other colleagues, published a 400-page study for the U.S. Arms Control and Disarmament Agency about the military dangers posed by the international spread of nuclear activities. "Moving Towards Life in a Nuclear Armed Crowd?" is credited with influencing changes in U.S. energy export policies.

Mrs. Wohlstetter also was a member of the Council of Foreign Relations, the International Institute for Strategic Studies and the Defense Science Board, and she served on the advisory board of the National Intelligence Study Center.

She was born in Duluth, Minn., graduated from Vassar College and received a master's degree from Columbia University in criminal psychology in 1936 and another master's degree in comparative literature from Radcliffe College in 1937.

Such disparate interests were connected because, as a student of both Hamlet and criminals, "she was fascinated with decision-making and ambiguity," said her daughter, Joan Wohlstetter-Hall of New York. "She was a master interviewer, a mild person who was a very good listener. .

. . [She and her husband] believed that with careful study, it was possible to change policy to better policies. They were driven to better the course of things."

Survivors also include a brother and a granddaughter.