After the Franco-Prussian war in 1870, The Kingdom of Prussia integrated with Bavaria, Wuertemburg and Baden to form Germany.

The best example I can think to give is the United States being formed after the Revolutionary war, discarding the Articles of Confederation and adopting the constitution, the unification of both centralized governance and while the US states (and the German Kingdoms) were formerly, theoretically part of a confederacy, they functionally acted as independent actors on the world stage.

Anyways, they were de facto equals, but de jure, Prussia ran the show.

Flash forward to World War 1, Germany and its army (Still referred to as the Prussian army, most professional soldiers were called "Prussians" in reference to the kingdom's military tradition), The abolishment of the German monarchy made way for one of the most liberal republics the world had ever seen at that point. A particular Austrian would take power 20 years later, but until then, many Germans harbored monarchical sympathies and longed for past glory. Whether the election of the Nazis was a manifestation of this longing, I'm not to say, but there's a pretty strong case that Germans once again desired a strong, centralized leadership headed under a glorious leader as they had been led historically.

Upon losing World War 1, Germany had lost West Prussia to Poland, one of the primary reasons Hitler invaded Poland in the first place was to retake West Prussia- particularly Danzig. Upon their defeat, East Prussia was given to the Soviet Union (now Kaliningrad) and West Prussia remained in Polish hands.

After World War 2, Germany were ousted from Romania, Czechslovakia, Poland and to a lesser extent, other Baltic and Slavic nations. The most bloody incidents occurred in Prussia, where they were deported across the world. However, upon hearing of the Red Army's march across Europe and the atrocities they were committing, many had already left. About 300,000-2,000,000 Germans died in these deportations.

Upon the end of World War 2, the Kingdom of Prussia (called "The Free State of Prussia" after World War 1) within Germany was dissolved by the allied powers, as the historical quality of Prussianism (unquestioned obedience to authority, and qualities associated with it) was thought to be a primary cause of World War 2's beginning and by extension, the holocaust.

Prussian diaspora still exists to this day. You can find some people calling themselves "Prussian" (most just call themselves German at this point) most prevalent in Australia, Argentina, Brazil, Chile and the United States. Many of these people ended up there after the expulsions.

This of course, is a brief overview. I'd urge you to delve deeper, or for somebody else to post a more concise answer. I guess it just caught my attention because I myself am Prussian, so I thought I'd just type from what I've read and learned.

edited: I use a lot of parenthesis, it makes it an eyesore.

One way to make sense of the role played by Prussia in European history is to compare the multiple meanings of the word "Prussian" to those of the word "Yankee."

Within New England, the use of the term "Yankee" is restricted to persons descended from the early English settlers of that region. In the northern states of the United States, it refers to anyone from New England. In the United States as a whole, anyone from places north of the Mason-Dixon line qualifies as a "Yankee." In the world as a whole, the term is applied to anyone from the United States.

A hundred years ago, the term "Prussian" could apply to someone who came from the provinces of East Prussia and West Prussia, to any person from the eastern parts of the Kingdom of Prussia, to any subject of the Kingdom of Prussia whatsoever, to any person from the northern parts of Germany, or, to any German, regardless of his immediate sovereign.