In East Prussia, the Poles brought the Teutonic Knights in to deal with the Old Prussians, a pagan tribe the Poles couldn’t handle.
As you say, the history often cuts in all directions.
Prior to about 1600 the Poles were a conquering and imperialistic nation, especially in the Ukrains. Now they have developed a victimology (much of it fully justified) about as extensive as any other people, with the probable exception of the Jews.
The collapse of the Polish-Lithuanian Commonwealth was one of the great tragedies of Europe.