Polonization (Polish: polonizacja, polszczenie) State policies relied mainly on emphasizing the Polish language in education and promoting its use in the country. The proponents of this policy hoped that it would result in the Polish language becoming more popular over the continuum of a few generations. Given the short time span in which they were applied, these policies, applied with varying intensity, contributed to increased ethnic tensions which led to large scale violence during World War II.

Historic periods
Between the 12th and the 14th centuries many Polish towns adopted the so-called Magdeburg rights that promoted the towns' development and trade. The right were usually granted by the king on the occasion of the arrival of the colonists from Germany. After the years of living amidst the Polish majority of western and central Poland those groups integrated with the larger community. A similar process of Polonization took place in case of merchants who settled there, especially Greeks and Armenians. They adopted most aspects of Polish culture but kept their Orthodox faith. Since the Middle Ages, Polish culture, influenced by the West, in turn radiated East, beginning the long and uneasy process of cultural assimilation.

Piast Poland
In the Polish-Lithuanian Commonwealth, the non-Polish ethnic groups, especially the Ruthenians and Lithuanians, found themselves under the strong pressure of Polish culture.
During all time of existing of Commonwealth Polonization in western part of country referred to rather small groups of colonists, like Bambrzy in Greater Poland.

Polish-Lithuanian Commonwealth
Polonization also occurred during times when a Polish state didn't exist, despite the empires that partition Poland applied the policies aimed at reversing the past gains of Polonization or aimed at replacing Polish identity and eradication of Polish national group. the situation for Polish culture steadily worsened.

Partitions
By the times of Second Polish Republic (1918-1939) much of the territories controlled by Poland over a century ago (at the Commonwealth's time), that were historically mixed (partly Ruthenian and partly Polish), had the Ukrainian and Belarusian majority..