I will add something about this Bambers who prefered to be Polish.
http://en.wikipedia.org/wiki/Bambrzythey still exist in Poland
Bambrzy (Poznańskie Bambry, German: Posener Bamberger) are the Poles of German origin, the descendants of Germans who moved from the area of Bamberg
The Polonisation of this group was a voluntary act and happened very quickly. The settlers refused to build their own churches, prayed with Poles, and their children learned the Polish language. There were also many mixed marriages with Poles living there. At the end of the 19th century, during the Kulturkampf period, all Catholics in villages inhabitated by Bambrzy chose Polish nationality during Prussian and German censuses. In the late 19th century, the meaning of the word "Bamber" (singular form) became wider - it started to denote all people living in those villages, regardless of their ethnic or cultural background.
Many of them were soldiers of the Polish army fighting in Great Poland Uprising. During the German occupation of Poland most of them, just as most Poles, were persecuted for their Polishness
What I want to say, some ethnic Germans decided to be Germans durring WWII and those who prefered to be Poles ... were Poles. and haven't been expeled after WWII. (I am not trying to prove that we are ... I am not Russian).
Just show Polish reality durring WWII, and that it was multicultural state and durring wars not everybody decideds to be loyal for host country. The fact is that some people were loyal.