Poland in 1939 COULD have held off the Germans at the rivers and the southern mountains as you say, bravo whiskey, but then the Soviets invaded and crushed that - or as NorseViking would say, the Soviets “liberated eastern Poland to join the glorious motherland”
Don’t be manipulative. I am clearly talking about 1920 and not about 1939.
And as for your ‘Poland taking back its land’ I fail to see it as any different than ‘Soviets took back the Russian Empire’. In the Soviet case in 1920 excluding unwilling territories.