Ezra F. Vogel, an eminent scholar of East Asia at Harvard University whose writings about modern politics and society in China and Japan helped shape how the world understood the rise of those two Asian powers, died on Sunday in Cambridge, Mass. He was 90.

The death, in a hospital, was confirmed by his son Steven, who said the cause was complications of surgery.

In 1979, as Japan was ascending as an economic power, Professor Vogel published the book “Japan as Number One: Lessons for America.” It was a provocative title for a nuanced book, in which he outlined in no-nonsense prose how and why Japan had caught up with, and in some cases surpassed, the United States. Among the reasons he cited were Japan’s ability to govern and educate its citizens efficiently and to control crime.

Two decades and several books later, Professor Vogel embarked on a comprehensive survey examining the economic transformation of yet another ascendant Asian superpower: China.

“In 2000, when I was thinking about what book to write to help Americans understand what was going on in China, I thought the most important thing was this new policy starting in December ’78 of opening and reform,” he recalled in a lecture last year at Ohio Wesleyan University, his alma mater. “I felt the way to describe that was to tell the story of the leader who led that.”

The result was an 876-page book about Deng Xiaoping, one of the most in-depth biographies to date of the pragmatic leader who shepherded China out of the chaos of the Mao years and pushed through reforms that helped lift hundreds of millions of Chinese out of poverty. Published in 2011, “Deng Xiaoping and the Transformation of China” drew on a decade of research and interviews with the notoriously private children of key Communist Party figures like Zhao Ziyang, Hu Yaobang and Deng himself. Professor Vogel also interviewed the former Chinese leader Jiang Zemin.

The book won the 2012 Lionel Gelber Prize and was a finalist for the National Book Critics Circle Award for biography, among other honors. But it also drew criticism from some who said Professor Vogel had been too forgiving in his assessment of Deng, including of the leader’s role in the bloody 1989 crackdown on pro-democracy protesters around Tiananmen Square in Beijing.

Professor Vogel defended his work in a 2011 interview with The New York Times. “This is unfair, because in some places I’m very critical,” he said. “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.”

Both “Japan as Number One” and “Deng Xiaoping” had been written with American readers in mind, and both sold well in the United States. But it was with Japanese and Chinese readers abroad that the books most resonated: Professor Vogel had held up a mirror to their countries, allowing them to examine the transformation of their societies in a new light.

In Japan, sales of “Japan as Number One” dwarfed those in the United States and the book became a favorite topic of Japanese television talk shows

“It was perfect timing,” Glen S. Fukushima, a senior fellow at the Center for American Progress in Washington and a former graduate student of Professor Vogel, said in a phone interview. “For a Harvard professor to publish a book saying ‘Japan as number one’ — it made him quite famous.”

In China, “Deng Xiaoping” became a best seller, even though several passages of the book were excised or altered by government censors. Chinese readers devoured the book and reportedly snapped up 500,000 copies upon its release in the country in 2013.

In a sign of Professor Vogel’s wide-reaching influence, condolences were conveyed by Chinese figures across the political spectrum upon word of his death, including from a former Tiananmen Square student protest leader and a spokesman for China’s foreign ministry.

“Professor Ezra Vogel has made unremitting efforts to promote communication and exchanges between China and the United States and enhance mutual understanding between the two peoples,” Wang Wenbin, the foreign ministry spokesman, said at a news briefing, calling Professor Vogel “an old friend of the Chinese people.”

Ezra Feivel Vogel was born on July 11, 1930, in Delaware, Ohio, to Joe and Edith (Nachman) Vogel, Jewish immigrants to the United States. His father ran a men’s and boys’ clothing store in town. His mother was a stenographer and journalist who later worked as the bookkeeper and cashier at the store.

After graduating from Ohio Wesleyan University in 1950, Professor Vogel served for two years in the Army. He then enrolled in a Ph.D. program in sociology at Harvard, where he studied the American family. Midway through the program, he was challenged by Florence Kluckhohn, a Harvard anthropologist and one of his thesis advisers.

“She said to me, ‘You’re so provincial, you’ve never been out of the United States, how can you talk about American society if you don’t have anything to compare it with?’” he recalled in the 2019 Ohio Wesleyan lecture.

Professor Vogel and his wife at the time, Suzanne Hall Vogel, who later became a researcher of Japanese culture, soon packed their bags and left for Japan.

The young couple embedded themselves in a Tokyo suburb, interviewing six families about once a week for a year. The resulting book, “Japan’s New Middle Class” (1963), documented the emergence of the office worker, or “salaryman,” as well as everyday family life in postwar Japan. It became an instant classic.

Upon returning to the United States in the early 1960s, Professor Vogel briefly worked as an assistant professor at Yale University. But with the drawdown of the McCarthy era, new opportunities were emerging for scholars to study China. Soon Professor Vogel was at Harvard, where he studied Chinese language and history as a postdoctoral fellow from 1961 to 1964. He rose to become a lecturer in 1964 and a professor in 1967.

He held various positions at the university over the years, including co-founder and director of the Program on U.S.-Japan Relations from 1980 to 1987 and director of the Asia Center from 1997 to 1999. In 1993, he took a two-year leave of absence from Harvard to serve as the national intelligence officer for East Asia at the National Intelligence Council in Washington. He retired from teaching in 2000.

Throughout his tenure at Harvard, Professor Vogel sustained a wide network of young scholars, including what became known as the “juku” (study group in Japanese), which often brought Japanese students together at his home in Cambridge.

Thomas B. Gold, a former student and a retired professor of sociology at the University of California, Berkeley, recalled convening in the converted attic of the professor’s home for seminars over instant coffee.

“He would be the first one to sit on the floor,” Professor Gold recalled. “I couldn’t believe how unpretentious he was, a big shot like him at Harvard.”

Over six decades, Professor Vogel frequently traveled to Asia, meeting with people from a diverse range of backgrounds and delivering lectures in Chinese and Japanese.

As a scholar, Professor Vogel refused to be penned in by methodology, and was largely uninterested in elegant theories or quantitative modeling. For his first book on China, published in 1969, he relied primarily on studying newspapers and conducting interviews in Hong Kong with refugees who had escaped from nearby Guangzhou to paint a picture of the region under Communism. For another book, “One Step Ahead in China” (1989), he was invited by government leaders in Guangdong to see firsthand how the post-Mao economic reforms were being implemented at the local level.

He published his last book, “China and Japan: Facing History,” in 2019 at the age of 89, expressing hope that the book — a review of the history of political and cultural ties between the two countries over 1500 years — would help improve understanding in that tense relationship.

He had been working on several projects at the time of his death: his personal memoirs; a book about Hu Yaobang, China’s popular pro-reform leader; and a paper, written with the Harvard political scientist Graham Allison, containing recommendations for the new presidential administration on how to improve Sino-U.S. relations.

Professor Vogel’s first marriage ended in divorce. In addition to his son Steven, a political science professor and Japan specialist at the University of California, Berkeley, he is survived by his second wife, Charlotte Ikels, whom he married in 1979; another son, David; a daughter, Eve Vogel; a sister, Fay Bussgang; and five grandchildren.

Like many other longtime China scholars, Professor Vogel had watched the recent downward spiral of U.S.-China relations with dismay.

And yet he remained optimistic.

In 2018, Zhao Wuping, deputy chief editor at the Shanghai Translation Publishing House, was airing concerns to Professor Vogel that it was becoming increasingly difficult for the publishing industry in China to translate and publish works by American authors.

Professor Vogel interjected with some words of encouragement.

“You will definitely experience some difficulties in this area,” Mr. Zhao recalled him saying. “But don’t lose your confidence; you are doing the right thing.”

He added, “We must be patient.”

Amy Chang Chien contributed reporting.