Looking back on the consequences of World War II, one might easily presume that the war spelled inevitable doom for the European empires that had dominated the globe at the war’s outset. But in 1945, the fates of those empires were far from obvious to many of the colonizers and the colonized. Two of the West’s most famous 20th-century heroes, Winston Churchill and Charles de Gaulle, were leading the charge in reasserting European imperialism in lands whence the Axis powers had driven it. American lectures about the virtues of decolonization merely convinced them that the Americans were naïve meddlers.

Historians writing about Britain’s Asian colonies after World War II usually concentrate on India, which is not surprising given that country’s magnitude and potential. The British, though, also attached great importance to their holdings in Southeast Asia — Burma, Singapore, Malaya, and the other states that eventually made up the Malaysian federation. Postwar British political leaders of most persuasions viewed the Southeast Asian colonies as essential ingredients of the empire, owing to their abundance of natural resources. As the rumblings of independence began to be heard from India, the British increasingly looked to Southeast Asia as the empire’s future Asian bulwark.

Historians Christopher Bayly and Tim Harper chronicle the ensuing struggles for Britain’s Southeast Asian colonies in “Forgotten Wars: Freedom and Revolution in Southeast Asia” (Harvard University Press, 554 pages, $35), the sequel to their much-praised history of Britain’s Asian empire during World War II, “Forgotten Armies: The Fall of British Asia, 1941—1945.” Primarily a diplomatic and political history rather than a military history, the new book focuses on the causes of armed conflict. After Japan’s capitulation, Messrs. Bayly and Harper contend, Southeast Asia remained in a state of war for the same reasons it had entered into such a state: poverty, imperialism, and ethnic, religious, and ideological conflict.

The authors have mined a very large number of sources. Most of their new historical unearthing can be found in the intricacies of Southeast Asian politics, which they describe in great detail and with careful nuance. Those deeply interested in the politics of Burma or Malaysia or other Southeast Asian countries will find much to delight them here. For other readers, the mounds of detail may become excessive. Another strength of the book is the authors’ employment of the perspectives of ordinary citizens.

Messrs. Bayly and Harper advance the familiar argument that the Japanese victories over the British in 1941 and 1942 destroyed the prestige of the white man in the eyes of the Southeast Asians and inspired anti-colonial movements. In analyzing Southeast Asian politics after the war, the authors pay closest attention to radicals who sought to oust the British. Conservative nationalists, moderate nationalists, religious activists, and other non-radicals receive considerably less attention, which is unfortunate because these groups profoundly influenced events in postwar Southeast Asia, and usually in more positive ways than the radicals.

Messrs. Bayly and Harper find little to admire and much to dislike in the British imperialists. The British leaders in Southeast Asia largely appear as arrogant fools who failed to understand the native peoples because of racism or ignorance. Some are seen to be exploiting the colonies strictly for economic reasons. Others, including Labour leaders such as Clement Atlee, favor colonial rule as a means of alleviating the poverty of the natives or spreading Christianity and Western civilization, but Messrs. Bayly and Harper view them as scarcely better, because of their paternalism. Among the specific transgressions of imperial rule emphasized by the authors are the raping of Southeast Asian women by Indian troops working for the British, the racial stratification that put Europeans above Eurasians and Eurasians above Asians, and the misidentification of subversives by colonial security forces.

The authors’ opinions of the British are unduly low. This can be seen most clearly by examining Britain’s influence upon the ultimate fates of Burma and the Malaysian states. In 1948, Burmese radicals rushed Burma to independence and kicked out the British. They nationalized British businesses and shunned the British experts who possessed experience in running the country. Burma, which many hoped would set an example for Asian economic advancement, became an impoverished dictatorship.

Singapore, Malaya, and the other lands that eventually joined the Malaysian federation, on the other hand, were led by moderates and conservatives who accepted a lengthier period of colonial control and cooperated with the British before and after independence in economic development and counterinsurgency warfare against the Malayan communists. Their collaborative relationship, as Messrs. Bayly and Harper acknowledge, set the stage for the spectacular economic growth in Malaysia and Singapore in the late 20th century.

The British, in Southeast Asia and elsewhere, were not generally foolish in their imperialism. Had they been ignorant imperialists, they could not have controlled vast swaths of the earth with little detachments of British troops. While some may find it comforting to condemn their paternalism toward indigenous peoples, the British have a better record of influencing these peoples than Americans, who assume that inside every foreigner is an American trying to break out. Given the current predicaments in which America finds itself, we would do well to spend more time searching British imperial history for lessons.

Mr. Moyar is the author of “Triumph Forsaken: The Vietnam War, 1954-1965.”