This is nonsense. Poland is a NATO member state. If Warsaw was attacked by Russia, it would trigger article 5 of the treaty, effectively declaring war on all member states. If the attack was carried out with a nuclear weapon, there would likely be a retaliatory strike. Voila, WW3.

Furthermore, however insane any leader of a nuclear power may be, I just got to believe there are competent, clear-headed people in the chain of command who would refuse to follow suicidal orders while not under immediate attack themselves.