Though far weaker and poorer than the mighty United States or the British Empire, China played a major role in the war. Some 40,000 Chinese soldiers fought in Burma alongside American and British troops in 1944, helping to secure the Stilwell Road linking Lashio to Assam in India. In China itself, they held down some 800,000 Japanese soldiers.

The costs were great. At least 14 million Chinese were killed and some 80 million became refugees over the course of the war. The atrocities were many: the Rape of Nanking, in 1937, is the most notorious, but there were other, equally searing but less well-known, massacres: the bloody capture in 1938 of Xuzhou in the east, which threatened Chiang’s ability to control central China; the 1939 carpet bombing of Chongqing, the temporary capital, which killed more than 4,000 people in two days of air raids that a survivor described as “a sea of fire”; and the “three alls” campaign (“Burn all, loot all, kill all”) of 1941, which devastated the Communist-held areas in the north.

These strains placed immense pressure on what by then was a weak and isolated country. But some of the Chiang government’s policies made matters worse. A decision to seize the peasants’ grain to feed the army exacerbated the 1942 famine in Henan Province. “You could exchange a child for a few steamed rolls,” one government inspector recalled in his memoir. Such missteps made the Nationalist (Kuomintang) government seem corrupt and inefficient, and an embarrassing ally for the United States — even though the Nationalists did the vast majority of the fighting against Japan, far more than the Communists.

When the Allies won in 1945, China’s contribution to the victory was rewarded with a permanent seat on the Security Council of the new United Nations, but little more. After a civil war, the Chiang regime fell to the Communists in 1949, and Mao had little reason to recognize its contributions to the defeat of Japan. China’s wartime allies also did little to remind their own people of its role in their victory: The Nationalist regime — which fled to exile in Taiwan — was an embarrassing relic, and the new Communist regime was a frightening unknown. For the West, China had gone from wartime ally to threatening Communist giant in just a few years.

One major consequence that remains of great relevance today is that the old enemies of Asia never struck a multilateral settlement of the sort that took place in the North Atlantic after 1945, with the formation of NATO and what has become the European Union. The United States’ decision to put China on the sidelines of the postwar world order it dominated has meant that China and Japan never signed a proper peace treaty. And it has meant that for many years Western historians treated China’s role in World War II as a sideshow.