Or, as I've heard elsewhere, the unification of all the Germanies.
Prussia is a "was," not an "is."
In the early 1970s I knew a girl from Hamburg, Germany whose mother came from Königsberg in East Prussia. She said that Prussians were known as the Italians of the north because of their love for art and music. Interestingly, her husband was from Austria, at the opposite end of the German-speaking world.
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The Teutonic knights were initially hired to come and protect a Polish Dukes territories from the Pagans. They were given a swath of land in exchange, and eventually took over.