His thesis: The U.S. government staged the Sept. 11, 2001, attacks on New York and Washington to justify wars in Afghanistan and Iraq. It is a tentative theory, he admits, based mostly on his doubt that Osama bin Laden's al Qaeda terrorist group launched the attacks.

"That's something that is simply 99% false," he said at a reading of his book on the second anniversary of the attacks.

A crackpot? A conspiracy theorist who believes that Elvis lives and the CIA murdered Kennedy? Not exactly. Mr. von Bulow, 66 years old, is a former German cabinet minister, a trim, silver-haired man whose book comes from one of the country's most prestigious publishing houses and who lectures at well-known public institutions.

He's not alone: In recent months, Germany's leading broadcaster, ARD, ran a purported documentary making similar claims, while half a dozen other German authors have published like-minded books.

"If we are being asked to participate in a new world war that's going to last years, then I expect that the cause of [the Sept. 11 attacks] be explained in the minutest detail," Mr. von Bulow told a crowd of 500 at the re ading at Munich's Literaturhaus, which often hosts famous authors. "What we have received is a joke. I've just put together the things that don't match up."

Conspiracy theories have long been part of the discourse in some parts of the globe, especially in places where a muzzled press and political repression warp public debate. Wild conjectures have also flourished on the per imeter of Western societies, with mini-industries devoted to plots alleged to have surrounded certain events. But over the past two years, improbable theories about the Sept. 11 attacks have attracted serious attention in some Western countries, often in direct proportion to the sinking credibility given to the U.S. and its motives in international affairs.

In Britain, cabinet minister Michael Meacher, who resigned from office this month, published a blistering attack in the Guardian newspaper, implying that Washington was involved in the attacks to justify a more-interventi onist foreign policy.

In France, Italy and Spain, authors have hit the bestseller charts over the past year by claiming that the U.S. is hiding the truth about 9/11.

In most European countries, conspiracy theories have remained the domain of a fringe minority, with even bestsellers vanishing from the public forum after a brief flash in the limelight. In Germany, however, the theories have had legs, and over the past few months, wave after wave of improbable and outrageous assertions have received serious hearings.

A recent public-opinion poll, by forsa, one of Germany's leading polling organizations, found that one in five Germans believes "the U.S. government ordered the attacks itself.

"The credibility given these theories has become so pronounced that the country's leading newsmagazine, Der Spiegel, ran a cover story earlier this month, giving a point-by-point rebuttal to the most widely spread myths. Among them: that Jewish people stayed out of the World Trade Center on Sept. 11, 2001, because they had been tipped off. ARD had to backtrack on its alleged documentary, later identifying the program's producer as a propo nent of conspiracy theories whose ideas weren't accepted by experts. A leading newspaper, the Suddeutsche Zeitung in Munich, published a lengthy piece this month called "Fools of Fear," ridiculing the ideas."I got more than 300 e-mails -- mostly hate e-mails -- after writing the article," said Hans Leyendecker, who wrote the piece. Conspiracy theorists, he says, are "having so much success. We had to do something to counteract it."

The spread of such theories about Sept. 11 is especially striking because Germans have long been among the most pro-American societies in continental Europe. While countries such as France have a tradition of skepticism o f the U.S., Germans have generally approved of U.S. leadership in the world, according to public surveys.But over the past year, German opinion has turned, according to two independent foreign-policy organizations, the Ge rman Marshall Fund and the Chicago Council on Foreign Relations. In an annual study released earlier this month, the organizations reported 45% of Germans think the U.S. ought to have the leading role in the world, down f rom 68% the year before. During the same period, support for the Bush administration's foreign policy also fell, to 16% from 26%.The shift may be due in part to an administration in Washington that is unpopular in Germany -- declarations after the attacks that the world was either with the U.S. or against it struck some here as polarizing and arrogant. So, too, did U.S. charges that Germans hadn't done enough to hunt down the alleged 9/11 attackers, some of whom had lived in Germany. But home-grown factors also seem to be at work. Since the reunification of East and West Germany 13 years ago, many Germans no longer want to follow the U.S. lead in world af fairs.

The war in Iraq was a turning point. Right after the Sept. 11 attacks, German Chancellor Gerhard Schroeder pledged "unlimited solidarity" with the U.S. and sent German troops to help out in Afghanistan. But when success i n Afghanistan was followed quickly by U.S. plans to confront Iraq, Germans had second thoughts.

"Somewhere between Kabul and Baghdad, we lost each other," said Ron Asmus, a senior fellow of the German Marshall Fund. "At the end of the day, we didn't just disagree on the policy but on the facts of what happened, and from that there was a jump to the conspiracy theories."

Recently, there have been efforts to patch up relations. President Bush met with Chancellor Schroeder last week and the two sides have pledged to work together to rebuild Iraq. But lurking beneath the diplomatic bonhomie is a suspicion in Europe's most-populous country that the U.S. is no longer the indispensable diplomatic partner it has been for the past half century.

Most of the conspiracy theories go far beyond a critique of Washington's preparedness before the attacks and its reaction afterward. Among the more startling ideas that are fit for discussion in Germany are: No planes cra shed in Pennsylvania or the Pentagon; detonations, not plane crashes, caused the World Trade Center to collapse; and U.S. intelligence, if it didn't outright plan the attacks, at least knew about them before they happened and decided to do nothing. Conspiracy theorists contend the motive for all this could have been to persuade isolationist Americans to intervene in world affairs -- just as they contend President Franklin Roosevelt used the Pearl Harbor attacks in 1941 to persuade Americans to enter World War II.

Few have profited more from Germans' changing view of the U.S. than Mr. von Bulow. From 1976 to 1980, he was one of the top officials in the West German defense department. In the 1980s, the Social Democrat served as mini ster for science and technology under Chancellor Helmut Schmidt. In 1994, when he retired from parliament after 25 years of service, he was the longest-serving member of parliament from his state.Mr. von Bulow then began writing, on such issues as the role of intelligence in the Cold War.

After Sept. 11, he had doubts, he says, about the source of the attacks. "Muslims wouldn't do this because they would know that it would hurt the Muslim world," he says.For a year, he says, he gathered information, taking most of it from Internet sites. His book contains many of the same ideas found in a bestseller from France last year called "The Big Lie."

This summer, just as German outrage over the war in Iraq was starting to boil, Mr. von Bulow came out with his book, "The CIA and the 11th of September, International Terror and the Role of the Secret Services." It has so ld more than 90,000 copies, hitting No. 3 on Der Spiegel's nonfiction bestseller list last week.

Like most skeptics, Mr. von Bulow is careful to phrase his ideas in the subjunctive. "Could haves" and "might haves" are sprinkled liberally throughout his book. But he is among those who question whether planes crashed i nto the Pentagon or Pennsylvania and suggests that they might have been staged to whip up popular outrage. He implies that the alleged hijackers who were on those planes could still be alive.When asked directly about the matter, he declined to elaborate on or explain his theory. "I simply listed in my book many questions," he says, during an interview at his home in a leafy suburb of Bonn.

It's a line repeated by others. "We are fighting a war on the basis of this attack, so we should get some answers," says Gerhard Wisnewski, a freelance TV producer, who made "Unsolved Case 9.11," which appeared on ARD, a publicly run German broadcaster. In a subsequent broadcast shown on the same network, Mr. Wisnewski was presented as a proponent of conspiracy theories.

"We don't claim to know what happened," says Ekkehard Sieker, producer of another program alleging U.S. manipulation of 9/11 facts, which ran on "Monitor," one of Germany's leading television news shows. "But we demand th at those who claim to know answer these questions. Otherwise, we can't believe them.

"The well-known institutions that have given the conspiracy theorists a forum say they did so in the spirit of open discussion. The prestigious Piper Verlag in Munich, which published Mr. von Bulow's book, said in a state ment: "The public interest and the debates justifies the questions and opinions of the author. They are a contribution to the democratic process of forming opinions."

Likewise, a spokeswoman for the television network that produced the program that ran on ARD said: "We should have the courage to bring controversial theses to the public and to discussion."

Another profiteer of the conspiracy theories has been Zweitausendeins, a book chain and publisher that has a knack for latching onto hot topics. The company devoted several pages at the front of its recent catalogue to bo oks and videos questioning the source of the 9/11 attacks. It even published some books itself. "Our publisher stands behind the content, or else he wouldn't have published it," a spokeswoman says.

At Mr. von Bulow's reading at Munich's Literaturhaus, not all those in the audience agreed with, or were familiar with, his specific charges. He seemed to win favor with his more-general claim that the U.S., once a model for postwar Europe, has become an unreliable state, from which Germans had best keep their distance.

"We Europeans shouldn't be arrogant. Each one of our countries has in the past tried to be the dominant world power," Mr. von Bulow said to murmurings of approval. "But I don't want to be dragged into another world war, o ne that will last for years and years."In conversations with a dozen visitors, one woman said she found Mr. Bulow's theories bunk, while others said they found them plausible."I can't believe all of it," said Daniel Feifa l, a 24-year-old architecture student. "That would destroy my belief in humanity. But that they knew about the attacks and let them happen because it could further their foreign-policy aims, yes, I'm prepared to believe t hat."

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--Special correspondent Almut Schoenfeld in Berlin contributed to this article.

Write to Ian Johnson at ian.johnson@wsj.com3 URL for this article: http://online.wsj.com/article/0,,SB106479068042179400,00.html