The division of Korea also brought about the phenomenon of illegal migration from the North to the South (as well as in the opposite direction). The nature of this migration has changed throughout the 70 years of division, and it seems that in the past 2-3 years we have witnessed another change. This four-part mini series deals with the four distinct periods in the history of this migration: 1945-1953, 1953-1990, 1991-2010 and 2011-present.