Poland never started wars man lol
21 border incursions on one night, and a mobilization of the army, in response to German attempts to negotiate a solution to the problems between them, even asking Britain to mediate? That sounds fairly provocative to me. How would Britain or France reacted if Germany was behaving thusly towards them?
It's not necessarily the first side to take decisive military action that bears the responsibility for wars.
Do you have any idea how reasonable Hitler's proposal was for the return of Danzig into the Reich? All he wanted was an extra-territorial corridor through the corridor, which he would allow Poland to keep in perpetuity! (Danzig, 95% German, and the "corridor" region (also mostly German) were taken from Germany by the Versailles Dictate -- which was recognized my most leaders and diplomats in the 20's and 30's as ridiculously unfair. It wasn't even a "treaty" as our schoolbooks call it, because it was imposed during a starvation blockade, and there were no negotiations.)
The Polish military leaders, emboldened by dishonest promises of protection from Britain, France (and encouragement from the US), and with an exaggerated sense of their ability to wage war against Germany, intentionally provoked Germany into action.
Germany, for her part, was surrounded by belligerent governments to the point that it was forced to sign a non-aggression agreement with its arch enemy, the Soviet Union. The French had spent most of the 30's trying to get another war going with Germany and sabotaging disarmament talks. (Few people realize that according to the terms of the Versailles Dictate, after Germany disarmed, other powers would be required to follow suit. And of course, they didn't.) From Germany's perspective, consider what it means when two countries with strong militaries, on geographially opposite sides of you, enter into a military alliance? How can that not be seen as threatening?
In short, the Brits and the French played the Poles to get their war going. Germany had wanted Poland as an ally, to work together to protect Europe against the Bolshevik hordes, and things were moving well in that direction. Hitler had signed a friendship pact with Pilsudski in 1934, bue he died in 1936 and relations thereafter got worse.
From what I've read the Germans seemed to have a lot of respect for the Polish military forces, and some considered them the best troops they faced in WWII.
Had Poland been under a rational government in the late 30's, I have no doubt Europe would've been spared that war, and the resulting decades of Soviet oppression of Europe.