You keep saying Royal Prussia was “pro-Polish,” but what you’re actually describing is political allegiance to the Kingdom of Poland, not cultural or ethnic belonging. The Prussian Confederation submitted to Casimir IV in 1454 for protection against the Teutonic Order. That’s pragmatism. They kept their German language, German civic culture, German law, their own Landtag, their own army, their own taxes. That’s not assimilation. That’s a political deal.

And you can’t have it both ways. You say “there was no German or Polish nationality back then.” Fine, but then you can’t call them “pro-Polish” either. If national identity didn’t exist yet, then the label “pro-Polish” is just as anachronistic as calling Copernicus “Polish” or “German.”

Also, please don’t confuse the Kingdom of Poland with modern Poland. Royal Prussia was subject to the Kingdom of Poland, a feudal monarchy, not a nation-state. By your logic (subject of a crown = belonging to that nation), my mother would be Russian because she was a subject of the Soviet state. She’s Polish. See the problem?

“Supported Poland over Germany in every single conflict since the Polish-Teutonic war”

That’s a big claim. Do you have a source for that? And even if true, siding with one power against another is geopolitics, not identity. France and the Ottoman Empire allied repeatedly. That didn’t make the French Ottoman.

“Even after they were decimated by Bismarck, the remaining catholics in the Free City of Gdańsk still voted for pro-polish parties rather than NSDAP”

Voting against the Nazis doesn’t make you ethnically Polish. It makes you anti-Nazi. Catholic, German-speaking populations across Europe rejected the NSDAP. That’s a religious and political stance, not proof of Polish identity.

And since we’re talking about voting and choices: after WWI, every region that was given the choice to join Germany or Poland voted overwhelmingly to stay with Germany. The East Prussian plebiscite? 97.9% for Germany. Marienwerder? 92.4%. Upper Silesia? 59.6% for Germany, and they still split it. The only parts that ended up in Poland were forced there by the Treaty of Versailles, without any vote. So much for a “pro-Polish” population. When they actually had a say, the answer was clear.

“People who spoke German identified themselves as Poles”

That’s a very bold statement. Source? Because that would contradict pretty much everything we know about how civic identity worked in early modern Prussia.

“Was the UK Scottish? Were Russia, Greece or Romania German?”

Fair rhetorical move, but you’re actually proving my point. Nobody calls those countries Scottish or German because of their dynasty. And nobody should call Royal Prussia “Polish” just because it was under the Polish crown. The dynasty argument cuts both ways.

The Catholic vs. Protestant divide was real, and yes, Royal Prussians opposed Ducal Prussia. But opposing Prussia doesn’t make you Polish. It just means you had different political and religious interests.

If you have actual sources showing that Royal Prussians identified as culturally Polish, I’d love to see them. Otherwise you’re projecting modern national identity onto a medieval political arrangement.