To more than 80 percent of Japanese voters, Prime Minister Junichiro Koizumi looks like a populist reformer. But to the American winner of the 2001 Pulitzer Prize for non-fiction, Koizumi is a "rightwing nationalist."

That was the eyebrow-raising assessment that Herbert P. Bix, author of "Hirohito and the Making of Modern Japan," made of Koizumi in a Op-Ed article published in the New York Times May 29.

Bix put himself into the dwindling ranks of perennial opponents of any change in the philosophy of unarmed pacifism embodied in Article 9 of the Constitution. His comments made it look like he saw a militaristic revival lurking behind almost everything Koizumi says.

The Binghamton University history professor even claimed that Koizumi wanted to make the Emperor head of state to "enhance the throne as an integrating force in Japanese life," although he offered no evidence to prove that Koizumi favors such a move.

To Bix, Koizumi's stated desire to eliminate the ambiguity about the constitutionality of Japan's Self-Defense Forces was a plot "to abolish the war-renouncing Article 9 even though its pacifist ideals are now broadly rooted in Japanese society."

"Like other rightwing nationalists, he (Koizumi) would have Japan assume military responsibility in world affairs," Bix warned.

Similarly, Bix ignored Koizumi's professed wishes to pay respects to Japan's war dead by visiting Yasukuni Shrine and mentioned only that Yasukuni enshrines "the spirits of several World War II war criminals."

Bix incorrectly wrote that "one of the first acts" of the new prime minister was to "sanction" history textbooks "celebrating Japan's pre-1945 imperial past." In fact, Koizumi merely noted that no legal procedure existed to change the textbooks after approval, which was given before he took office.

Bix's tirade was significant because it repeated a pattern of unsubstantiated conclusions and sweeping assumptions that marred his book about the Showa Emperor, notwithstanding its Pulitzer Prize.

The book is a landmark work of research and does succeed in destroying "myths" that the Showa Emperor was a pacifist and "always stood above politics." The Showa Emperor held political and military opinions and expressed them frequently, Bix showed with extensive quotes from participants in meetings with the Showa Emperor.

The book also details what Bix calls a "system of irresponsibility" in decision-making and a proclivity of the Army, the Navy and other bureaucratic bodies to act only to their own benefit while ignoring the interests of the nation. As such, it provides a historical background to the ineffectual governments of Japan's "lost decade" of the 1990s.

But on the central issue of whether the Showa Emperor himself made all -- or any -- of the decisions that were issued bearing his seal, Bix failed to produce convincing evidence.

Bix wrote that the Showa Emperor "sanctioned Japan's first military intervention in China," or "approved" a report, or "condoned the army's coverup," or "gave his consent to the army's dispatch," or "granted awards and promotions" to conquerors of Manchuria, or gave "permission" for action after action. But even an exhausting 82 pages of end notes offered no sources to prove that the Showa Emperor himself made the decisions that bore his name.

Indeed, Bix's book includes a photo caption that read "without uttering a word, he (the Showa Emperor) backed a stronger military policy toward China."

Bix provided detailed, documented descriptions of the decisions that lead to the attack on Pearl Harbor in 1941. But he also made clear that the decisions were already formulated when they were brought before the Showa Emperor, whom Bix described as reluctant and doubtful but nonetheless willing to give "his sanction." But the only evidence he offered that the Showa Emperor approved the attack came when Bix quoted a participant in the final meeting as saying "the Emperor nodded in agreement" as each clause of the directive to launch the attack was read aloud to the gathering.

The traditional vagueness of Japanese decision-making and the secrecy that the Imperial Household Agency imposes on its mountains of historical documents make it impossible to prove or disprove Bix's assessment that the Showa Emperor acted as a "commander in chief in every sense of the word." Bix, however, undermines his own judgment by acknowledging that the armed forces "honed a new entitlement -- "the right of supreme command" -- that allowed them to approve or overthrow Cabinets.

Most importantly, Bix dismisses any possibility that the Showa Emperor acted as a constitutional monarch.

"A real 'constitutional monarch' would not have believed that . . . the monarch (had) to approve every report of the Cabinet," he wrote. But again Bix offered no evidence that the Showa Emperor approved everything.

The Showa Emperor himself, in audiences with foreign correspondents in 1971 and 1975, declared that he had, throughout his rule, acted as a constitutional monarch, "as my grandfather, the Emperor Meiji, instructed me." Only twice, when he ordered mutinous solders to return to their barracks in 1936 when "the leaders of the government were missing" and could not make decisions themselves and when Prime Minister Kantaro Suzuki "entrusted me with the decision" to end the war in 1945 did he make decisions on his own, the Showa Emperor himself said.

Bix condemned the Showa Emperor for prolonging the war in the hopes of winning assurances of his own safety after defeat. But to Tomohiko Taniguchi, a senior writer of Nikkei Business, the Showa Emperor probably could not have made the decision to surrender if atomic bombs had not been dropped on Japan to create a sense of ultimate crisis. Taniguchi made that observation in a review of Bix's book in the May edition of the magazine "Insight Japan."

Bix himself wrote that the Showa Emperor sometimes "chose not to exercise his discretion to influence policy or to alter some planned course of action." Other historians could use that wording to describe how a constitutional monarch might act. And even Bix, on the last page of his book, concluded that the "national leadership" used the Showa Emperor for its own purposes.

Bix offered good advice by warning that future leaders of Japan should not be allowed to do it again. But he hit the wrong panic button when he sounded his alarm about Koizumi and present-day Japan.