Complex sentence: Thus, Polish communists found themselves unexpectedly at the head of a national liberation movement, and the enthusiastic public support offered to Gomułka contributed to the legitimization of communist rule in Poland, which managed to incorporate mass nationalist, anti-Soviet feelings into the prevailing power structures.
Split into simpler sentences: Thus, Polish communists found themselves unexpectedly at the head of a national liberation movement. The enthusiastic public support offered to Gomułka contributed to the legitimization of communist rule in Poland, which incorporated mass nationalist, anti-Soviet feelings into the prevailing power structures.