The entrance of Polish troops into the Ukraine, if it will not automatically trig the art.5, it would led to cascade of events, like a further Russian mobilization, then a Baltic mobilization, then an UK ultimatum that if the Polish territory is hit, then they intervene. But, why should Poland send troops in Ukraine? Why they can't continue like they are doing until now? For example, why they can't pick-up 100.000 troops, then "discharge" them all from the Army, so that they are free to go in Ukraine in order to privately fight for the freedom? Russia has already prouved to accept that.