https://warsawinstitute.org/poland-first-fight/
Poland was the first country to firmly resist the brutal expansion of the totalitarian powers that were utterly indifferent to the rights of weaker countries. Poland’s armed resistance to German aggression on September 1, 1939, was a turning point in world politics towards the Third Reich. Contrary to the hopes of Adolf Hitler, on the third day after the commencement of military operations the German attack on Poland transformed into a world war.