International Migration before 1945
Stephen Castles, Mark J. Miller
The Age of Migration·1998
The post-1945 migrations may be new in scale and scope, but population movements in response to demographic growth, climatic change and the development of production and trade have always been part of human history. Warfare, conquest, formation of nations and the emergence of states and empires have all led to migrations, both voluntary and forced. The enslavement and deportation of conquered people was a frequent early form of labour migration. From the end of the Middle Ages, the development of European states and their colonisation of the rest of the world gave a new impetus to international migrations of many different kinds.