During the "Deluge" of 1648-1667, Poland was invaded and largely overrun by Sweden and Russia, the latter supporting dissident Ukrainian rebels. http://en.wikipedia.org/wiki/Deluge_(history)
Yet, despite the quasi partition, Poland was able to raise new armies from (occupied?) territories, and drive out both the Swedish and Russian armies.
From 1772-1795, Poland was partitioned between Prussia, Austria-Hungary, and Russia. But until the third partition, Poland retained a core. The American Revolution hero Kosciusko was able to raise a Polish army, but not drive out the invaders, in 1794.
Why was Poland successful in resisting partition the first time but not the second tine around? Could the Deluge have weakened Poland enough to "set up" a partition a century later? Was the rising use of the liberum veto http://en.wikipedia.org/wiki/Liberum_veto a culprit? And my understanding was that in the 1790s that the Polish nobility was split into pro German and pro Russian factions; was that NOT the case a century earlier, between Russians and Swedes?