Until the middle of the Nineteenth Century, both China and Japan fended off Western imperialism in their different ways. Then Japan abruptly shifted course to imitate some aspects of Western states in order to preserve both its political independence and cultural identity. China lagged behind on making this necessary shift. Ultimately, a modernizing political movement, the Kuomintang (KMT, called the Nationalists by Americans) gained a rough control over China.
The results of historical events so briefly described proved harrowing for many millions of people. A semi-Westernized Japan pursued empire in China and Southeast Asia, then was smashed to bits in the Second World War. The Chinese Communists triumphed in the civil war with the Nationalists that followed the Second World War in Asia.
Communism’s victory in China wrong-footed wartime American plans for the postwar order in East Asia. Americans leaders (or at least Franklin D. Roosevelt) had envisioned Nationalist China as a new great power that would co-operate with Americans efforts to build a peaceful and prosperous Asia. Instead, the Peoples’ Republic of China aligned with the Soviet Union in the Cold War. The Korea War and the wars in Indochina followed. Only in the 1970s did the hostility begin to decline. Since the late 1970s, China has vigorously remodeled its economy into the second largest in the world and, more recently, sought a leading role in international affairs.
In these efforts, many things have been bent to serve the nation’s interests. One of those things has been History. One aspect of China’s historical revisionism has been China’s role in the struggle against Japan. Once upon a time, if they knew what was good for them, Chinese historians played down the role of the corrupt and incompetent Nationalist government while playing up the role of the Communists. Now, if they know what is good for them, Chinese historians have begun to argue for the importance of China’s resistance to Japan not only for China, but for the whole world. By resisting Japanese aggression from 1931’s Manchurian Incident to full-scale war from 1937 onward, China bought time for the Western countries to gather their wits and then their military resources. From 1941 onward, China figured as the chief battlefield and military opponent of Japan. From this point of view, the American combined arms offensive across the Pacific and the British counter-attack in Burma were side-shows.
In its struggle against Japan, China received little help from Western countries. After the war, China received little for the eventual victory over Japan. Now, suggest the Chinese historians, it is time for that bill to be paid by according China the leading role in Asia.
Probably they are taking their cue from Western historians who examined the roots of European appeasement policies in the 1930s. Those historians have argued that not moral rot, but strategic and economic realities hampered Britain and France from making an early stand against Hitler. They needed time to rearm or they would be defeated. Germany’s re-militarization of the Rhineland, Austria, and the Sudetenland were all necessary sacrifices in this delaying action. The difference is that Western historians have no policy agenda.
 For background, see: https://waroftheworldblog.com/2019/07/17/the-asian-century-5-17-july-2019/
 Rana Mitter, China’s Good War: How World War II Is Shaping a New Nationalism (2020), reviewed by Howard French, WSJ, 14 October 2020.
 For a counter-attack on this view, see Tim Bouverie, Appeasement (2019).