THE exchange of populations between Greece and Turkey of 1922-24 was unique in world history in its combination of four elements: first, this "swarming" of two human hives was compulsory and resulted from military events; second, no economic motives were directly involved, no impulse but that of nationalism; third, populations were uprooted which had been indigenous, in the one case for four centuries and in the other for thirty, and, finally, the scale was unprecedented.