> these poor people served as a "buffer" against the Mongols, saving Europe from the slaughter ...
You mean saving Western Europe :)
Mongols ran over (and did a lot of slaughter in) the most of Eastern and Central Europe, including Poland, Czechia, parts of todays Germany, Hungary, Bulgaria, Croatia and Austria. There was no "buffer" that stopped them, they've stopped eventually because their Great Khan died. As the leadership broke down and fights for power arose, they've been forced to return back home.
You mean saving Western Europe :)
Mongols ran over (and did a lot of slaughter in) the most of Eastern and Central Europe, including Poland, Czechia, parts of todays Germany, Hungary, Bulgaria, Croatia and Austria. There was no "buffer" that stopped them, they've stopped eventually because their Great Khan died. As the leadership broke down and fights for power arose, they've been forced to return back home.