Political cleansing of population refers to eliminating categories of people in specific areas for political reasons. The means can vary from forced migration to genocide.
Typical reasons
Some groups attempt to eliminate the base of support for political opponents, e.g., for insurgents. This happens in many countries with high levels of insurgency, such as Colombia. It may be a means for and referred to as "pacification".
As the Soviet Union annexed territory during the first half of the 20th century, including the Baltic States and parts of Poland and Romania, among their first actions was identification and removal of the social classes classified as "enemies of the working people". Methods of elimination included execution, imprisonment and deportation.
References
Political cleansing of population Wikipedia(Text) CC BY-SA