RUTHFULLY YOURS

Mr. Mitter’s book gives China its historical due. It chronicles the immense cost that China bore as it absorbed Japan’s 800,000-troop invasion beginning in 1937—two years before Britain and four years before the U.S. entered World War II—and deflected the brunt of the Red Sun’s destructive energies away from other theaters and Western armies. Some 14 million Chinese died as a result of the conflict. In the infamous Nanjing massacre of 1937, the Japanese 10th Army raped women en masse, used male civilians for saber practice, and set tied-together groups of 100 or more detainees afire with gasoline.

China also paid in other, less easily recognized ways. The fledgling efforts of the world’s most populous country to join the modern era through heavy investments in infrastructure and industrialization were swept away. Most of country’s rail network, sealed highways and factories were destroyed.

The main character of this book, which is filled with fascinating narrative subplots, is China’s Nationalist leader and wartime head of state, Chiang Kai-shek. Western ambivalence toward Chiang dampened war support for China. As the author writes, “Western condemnations of the Chinese war effort, and the role of the Nationalists in particular, have been based on accusations that the regime was too corrupt and unpopular to engender support: a popular American wartime joke declared that the Chinese leader’s name was really ‘Cash My Check.’ ” This wasn’t completely fair. “The truth was more complex: the Europe First strategy meant that China was to be maintained in the war at minimum cost, and Chiang was repeatedly forced to deploy his troops in ways that served Allied geostrategic interests but undermined China’s own aims.”

It is in this sense that wartime China can perhaps be said to have been lost, arguably more than once. Time and again, Franklin Roosevelt and his generals shrank from making decisive commitments in money, materiel and men to support the Nationalists, opening the way for advances by both the Japanese and Communist Party forces. Relations with Chiang were finally pushed over the brink by the Allied insistence that he commit substantial forces to stopping the Japanese takeover of Burma in 1942, which would have opened British-ruled India to similar attack. This was at a time when China itself was facing one of the biggest Japanese offensives of the war. “I’m certain that it’s American policy just to make use of us without any sincerity,” Chiang wrote at one point.

As Chiang’s hold on the country became increasingly tenuous, the U.S. sent exploratory feelers to Mao Zedong and his forces, which were based in the northern city of Yanan. American diplomats were briefly seized with a sense of opportunity about working with the Communists, who had impressed visitors with the order that prevailed in their main area of control. This moment wouldn’t last, though, and Washington snubbed Mao just as his Communists began moving into the ascendancy. The U.S. recommitted itself as a backer of Chiang’s by-then failing cause. In 1949, the Communists emerged victorious, and a year later Mao’s China and the U.S. would be fighting each other in Korea.

This book isn’t the first major work to partially rehabilitate Chiang Kai-shek. Jay Taylor’s “The Generalissimo” (2009) also offered a more sympathetic view. “Forgotten Ally” is anything but unidirectional revisionism, though. Mr. Mitter details Chiang’s indifference to the human costs of his wartime strategy. Chiang’s flooding of Yellow River Valley lowlands in 1938 to slow a Japanese advance, for example, ended up killing nearly a million Chinese. Chiang lied about the catastrophe and sought justification in the 5,000-year-long narrative of Chinese history. And like Mao, Chiang relied on an all-pervasive security apparatus to bolster his power. In reminding us of Chiang’s depravities, Mr. Mitter shows that the Communist catastrophes to come weren’t so much a break with China’s past as a continuation of it.

Mr. French teaches at the Columbia University Graduate School of Journalism. He is the author of the forthcoming “China’s Second Continent: How a Million Migrants Are Building a New Empire in Africa.”