Prussia and the Disappearing Germans

When Wellington defeated Napoleon at Waterloo in 1815 he was saved in the nick of time by the arrival of the Prussian army. But who were the Prussians and where was Prussia?
By 1815 Prussia was the major German state (with the exception of the Austrian Empire). Its capital was Berlin, which lay in Brandenburg, rather than old Prussia which lay to the east and is now occupied by Poles and Russians and Baltic people.
The original Prussians spoke a Baltic language, like the Estonians and the Finns, but during the Middle Ages they were conquered, colonised and Christianized by Germans from the west.
Eventually they were assimilated into German culture. Over the centuries German Prussians held their own against Poles and Russians and Swedes. They welcomed the Protestant Reformation, but later on they preferred to worship the state instead.
In the eighteenth century, under Frederick the Great, Prussia became a militarized bureaucratic state, fifty years before the French Republic. To instil habits of obedience the state usurped the role of parents by instituting compulsory education and by promoting moralism in the form of Pietism. The people were taught to equate 'good' with obedience to Authority.
Eventually this military state overcame Austria and France and spread westwards till it had absorbed all Germany.
Eventually, in the 1930s Prussia more or less lost its separate identity within Germany, and in the 1940s the old Prussian lands were lost to Germany entirely, being occupied by Poland and the Soviet Union.
All the Germans of Eastern Europe were expelled in one of the greatest acts of ethnic cleansing in history. It is estimated that 12 to 14 million Germans fled to the new countries of East Germany and West Germany, leaving their ancient homes not just in Prussia, but in Transylvania, Ukraine and Czechoslovakia too.
The refugees played a full part in the reconstruction and prosperity of post-war Germany.
They have also shared in Germany's decline. Far from expanding eastwards modern Germany imports millions of immigrants as it suffers demographic decline.
Each German woman produces on average 1.4 children, well below the replacement rate.
After centuries of dynamic expansion the Germans have disappeared from their Prussian homeland.
They replaced their faith and their families with militarism and bureaucracy. They diminished themselves and became Reichsdeutsche.
Having suffered terrible wars and catastrophic defeats, the Germans appear to be calling time on their great civilization.