I think one of the best example of ethnic cleansing and population displacements were in Poland around the IIWW:
- http://en.wikipedia.org/wiki/Massacres_of_Poles_in_Volhynia_and_Eastern_Galicia
- http://en.wikipedia.org/wiki/Flight_and_expulsion_of_Germans_%281944%E2%80%9350%29
Due to the massive population displacements (Polish nationality from territory seized in the East by Soviets and German nationality from territory given to Poland by allies in the West and North) Poland changed from multinatonal and multireligous country (with under 70% being Polish and Catholic) to a unified one-nation country with over 99% being Polish and Catholic.
Putting aside all the sorrows of the population involved it has to be said that this change lead to the vast stabilization of the internal relations within the country and vastly increased the overall security of the country.
- http://en.wikipedia.org/wiki/Massacres_of_Poles_in_Volhynia_and_Eastern_Galicia
- http://en.wikipedia.org/wiki/Flight_and_expulsion_of_Germans_%281944%E2%80%9350%29
Due to the massive population displacements (Polish nationality from territory seized in the East by Soviets and German nationality from territory given to Poland by allies in the West and North) Poland changed from multinatonal and multireligous country (with under 70% being Polish and Catholic) to a unified one-nation country with over 99% being Polish and Catholic.
Putting aside all the sorrows of the population involved it has to be said that this change lead to the vast stabilization of the internal relations within the country and vastly increased the overall security of the country.