Ezra F. Vogel, a Harvard professor who served as a bridge between East Asia and the United States, examining the rise of two superpowers — Japan and China — in books that drew wide acclaim on both sides of the Pacific, died Dec. 20 at a hospital in Cambridge, Mass. He was 90.

The cause was complications from colon cancer surgery, said his son Steven K. Vogel, a political scientist and Japan scholar at the University of California at Berkeley.

Though trained as a sociologist, Dr. Vogel drew on fields including history, psychology and anthropology, interviewing families, executives and top political officials in Japan and China. After decades in which China was largely closed off to the West, he was part of the first generation of American scholars to travel across the country, studying its society in the years after Mao Zedong’s death in 1976. In a tribute, the Foreign Ministry in Beijing called him “an old friend of the Chinese people,” according to the Associated Press.

“He had a rare combination of capabilities in studying both countries: deeply knowledgeable about their histories, societies, and politics, fluent in both their languages, and possessing a truly globe-spanning network of fellow scholars, government officials, and friends,” China scholar Michael D. Swaine said in an email.

Dr. Vogel wrote occasional opinion articles on foreign affairs and served in the Clinton administration for two years, briefing Cabinet members as East Asia officer on the National Intelligence Council. He was best known as the author of books such as “Japan as Number One” (1979), which suggested economic and political lessons the United States might learn from Japan amid a growing trade deficit, and “Deng Xiaoping and the Transformation of China” (2011), which won the Lionel Gelber Prize for best book on foreign affairs.

The latter was a National Book Critics Circle Award finalist and hailed as a definitive account of Deng, who oversaw sweeping economic reforms but was also blamed for the 1989 massacre of protesters at Tiananmen Square. In an interview with the New York Times, China specialist David Shambaugh called the book “a major accomplishment,” adding that “while much of this information is not necessarily new, this is the first time we’ve seen it all in one place, analyzed with scholarly detachment.”

Published when Dr. Vogel was 81, the book was the result of a decade spent digging through archives in the United States and Russia, traveling through China and interviewing Communist Party dignitaries such as former president Jiang Zemin, whom he had previously hosted during a 1997 visit to Harvard.

But the book was also criticized by scholars who accused Dr. Vogel of being overly sympathetic to his subject and failing to emphasize some of Deng’s human rights abuses. Dr. Vogel noted that he had been critical of Deng in some places, telling the Times, “A lot of Americans’ view of Deng is so colored by Tiananmen Square. They think it was horrible. I have the same view. But it’s the responsibility of a scholar to have an objective view.”

“Who in the 20th century had more influence on more people?” he added. “He took 300 million people out of poverty. They’d been trying to do it in China for 150 years, and they couldn’t. And he did it.”

Dr. Vogel’s work in East Asia began only by chance, as he was putting the finishing touches on his doctoral thesis at Harvard. He was writing about American families and mental health when his adviser, Florence Kluckhohn, told him he was too “provincial,” having never traveled overseas. “If you want to look at American society objectively,” she said, “you really have to go abroad to a different culture.”

Taking her advice, Dr. Vogel secured a fellowship in Japan, where he spent two years learning the language and conducting research for his 1963 book “Japan’s New Middle Class.” The book drew on the experience of six families in a Tokyo suburb, whom Dr. Vogel interviewed with his first wife, psychotherapist and social worker Suzanne Hall Vogel.

“You wanted to read the footnotes because they were so luscious — full of gems,” said his former student Merry White, an anthropologist and Japan specialist at Boston University. In a phone interview, she added that Dr. Vogel and another scholar, Ronald P. Dore, helped launch the field of modern Japanese studies, illuminating “the difference between official Japan and real life.”

Dr. Vogel later wrote “Japan as Number One,” which Swaine described as “the standard work analyzing Japan’s rise to become a major economic player in the world,” as well as a follow-up, “Comeback” (1985).

By then he had also turned his attention to China, having returned to Harvard in the early 1960s as a postdoctoral fellow at a time when the university was looking for young scholars who could focus on the country. Within a few years he traveled to Hong Kong, where he interviewed refugees from southern China for the book “Canton Under Communism” (1969).

Dr. Vogel later succeeded the pioneering China scholar John King Fairbank as director of Harvard’s Center for East Asian Research, now the Fairbank Center for Chinese Studies. He also chaired the university’s Council for East Asian Studies, co-founded the Program on U.S.-Japan Relations at Harvard’s Center for International Affairs and served as the founding director of the Harvard University Asia Center.

“For so many people he was not only a gracious, friendly person, but a model for what a scholar should be,” said Michael A. Szonyi, the Fairbank Center’s current director. Dr. Vogel sought to connect scholars from around the world and across disciplines, he said, often gathering colleagues and visitors for Chinese takeout meals at his home in Cambridge.

“At a time when scholarship was moving increasingly in a direction of narrow, disciplinary specialization,” Szonyi said, “he tried to bring together political scientists, sociologists, historians, even medical anthropologists, and to get us in conversation with each other.”

Ezra Feivel Vogel was born in Delaware, Ohio, on July 11, 1930, to Jewish emigrants from Eastern Europe. His mother was a homemaker, and his father ran a men’s and boys’ clothing store.

Dr. Vogel was 19 when he graduated from his hometown college, Ohio Wesleyan University, in 1950. He later served in the Army and received a master’s degree from Bowling Green State University in Ohio, followed by a doctorate from Harvard in 1958. He taught at Yale before returning to Harvard and retired from teaching in 2000.

His latest book, “China and Japan: Facing History” (2019), explored the strained relationship between those two countries and argued for closer ties. “It was a charming and optimistic project, which was never going to fully address the issues, but it made a positive contribution,” Szonyi said. “Even in his 80s he was asking himself, how can I contribute to making the world a better place?”

Dr. Vogel’s marriage to Suzanne Hall ended in divorce. Survivors include his wife of 41 years, Charlotte Ikels, a retired anthropology professor at Case Western Reserve University; three children from his first marriage, David Vogel of Cambridge, Steven Vogel of Berkeley and Eve Vogel of Amherst, Mass.; a sister; and five grandchildren.

Dr. Vogel was working on a biography of Hu Yaobang, a reform-minded Communist Party official, as well as a policy paper on the U.S.-China relationship that he had planned to submit to the new Biden administration. His interest in politics and history had picked up in recent years, after decades of scholarship in areas including family issues and industrial policy.

“He kept changing, and that was kind of marvelous. It allowed us to see that a scholar doesn’t have to have one song,” said White, his former student. “John Fairbank used to say you have one subject in your whole life, and you’re just going to keep repeating it. And Ezra wasn’t like that.”

“He wanted to have an impact,” she added, “and he wanted people to listen.”

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