What was repatriation and who was most affected by it?

Repatriation is the process of returning a person back to one's place of origin or citizenship. In the 20th century, following all European wars, several repatriation commissions were created to supervise the return of war refugees, displaced persons, and prisoners of war to their country of origin. 

It should be at the center of any map going vertically: the prime meridian, as it passes through greenwich,  england, is considered 0 degrees longitude