Poland's "Solidarity" was

Answer: it is a name of independent trade unions in Poland established in 1980 in Poland. But it true role was a social movement that started opposing to Communist party (the only party, state-party) in Poland.

Explanation: It contributed significantly to the fall of Communism in Poland (1990). It was not the only anti-Communist movement in Poland at that time, but it was the most important.

An independent trade union