From Orderly and Humane: The Expulsion of the Germans after the Second World War, by R. M. Douglas (Yale U. Press, 2012), Kindle p. 67:
The driving out of unwanted peoples, to be sure, is a practice almost as old as recorded history. The Old Testament tells the story of numerous forced migrations carried out by the Israelites and their neighbors against each other, the Babylonian Captivity being the most celebrated. Philip II of Macedonia was renowned for the scale of his population transfers in the fourth century B.C., a precedent that his son, Alexander the Great, appears to have intended to follow on a far more massive scale. The colonial era witnessed many more forced displacements, often accompanied or initiated by massacre. Some of these bore a distinctly “modern” tinge. The Act of Resettlement that followed Oliver Cromwell’s conquest of Ireland, for example, ordered Irish property owners in three-quarters of the island to remove themselves to the impoverished western province of Connacht by May 1, 1654, to make room for incoming English and Scottish colonists; those remaining east of the River Shannon after that date were to be killed wherever found. “The human misery involved,” in the judgment of Marcus Tanner, “probably equaled anything inflicted on Russia or Poland in the 1940s by Nazi Germany.” On a smaller scale, but proportionately just as lethal, was the United States’ forced relocation of part of the Cherokee nation from Tennessee, Georgia, and Alabama to eastern Oklahoma along the so-called “Trail of Tears” in 1838; perhaps a quarter of the fifteen thousand men, women, and children who were driven out perished, most of them while detained in assembly camps. Extensive forced migrations occurred in Africa and Asia also. In what is today Nigeria the Sokoto Caliphate, the largest independent state in nineteenth-century Africa, practiced slavery on a massive scale—by 1860 it possessed at least as many slaves as the United States—as an instrument of forced migration, the purpose being to increase the security of disputed border areas. “Enforced population displacement … was supposed to strengthen the Islamic state, which was achieved through demographic concentration.” On the western borderlands of China, the Qing Empire in the seventeenth and eighteenth centuries “used deportations and mass kidnappings to build a human resource base.”
Contemporary scholars agree, though, that the twentieth century has been the heyday of forcible population transfers. The rise of the nation-state, in place of the dynastic multinational empires of the earlier period, was both cause and effect of the ideological claim that political and ethnographic boundaries ought to be identical.