The Polish language became far more homogeneous in the second half of the 20th century, in part due to the mass migration of several million Polish citizens from the eastern to the western part of the country after the Soviet annexation of the Kresy in 1939, and the annexation of former German territory after World War II. This tendency toward a homogeneity also stems from the vertically integrated nature of the Polish People’s Republic.
The inhabitants of different regions of Poland still speak “standard” Polish somewhat differently, although the differences between regional dialects appear slight. First-language speakers of Polish have no trouble understanding each other, and non-native speakers may have difficulty distinguishing regional variations.
Polish is normally described as consisting of four or five main dialects: