Poland existed as a sovereign nation for many centuries before the Verseilles treaty, often much larger than in modern times. I will look into the 58,000 slaughtered Germans because I find that difficult to believe.
Here’s the source document for the alleged 58,000 German deaths.
It appears to be Nazi propaganda.
Pat Buchanan argues that the Germans did have a legitimate claim to Danzig (ethnically and historically German semi-autonomous City-State created by Treaty of Versailles), and that the Poles were willing to cede it until Churchill stepped in with an unequivocal British guarantee to defend Poland.
In other words, Buchanan argues, Churchill wrote a check he had absolutely no means of covering ... leading to a tragic turning point in world history.