Last weekend, in Chemnitz in Saxony, a 35-year-old German-Cuban was killed after an altercation with two asylum seekers, one Syrian, one Iraqi. Within 24 hours, the web was alive with images that suggested that the authorities were scarcely able to control the thousands of rightwing populist demonstrators who descended on the eastern German city. It was, said the business newspaper Handelsblatt, “an outpouring of hatred that shocked the nation”.

Shocked, but not surprised. For there is nothing new about the old East Germany shocking Germany. It has long been the received wisdom that Germany needs to take account of, and deal with, the real problems and genuine concerns of people in the old east. People have been saying this since the Saxons first shocked the newly reunited country in 1991. That year, after a week of violence in the small town of Hoyerswerda, about 230 asylum seekers were simply spirited away by the authorities at dead of night. For the neo-Nazis, it was an epochal victory, still celebrated: the state, they said, could not, or would not, resist a populist right prepared to use open violence.

More than €2tn has gone from the old West Germany to the old East Germany. But it hasn’t worked.

The answer was not to crack down on the populist right but to find simple explanations for their rise. Things were different in the east, so the line ran, because an entire generation had experienced occupation by the Soviet Union and because reunification itself had been hastily rammed through by Helmut Kohl, then badly handled by gung-ho free-marketers. The answer was a vast programme of aid.

Since 1990, more than €2tn has gone from the old West Germany to the old East Germany, not as a loan but as a subsidy. But it hasn’t worked. In 2004, years before the financial crisis and the new wave of asylum seekers, elections to the Saxon state parliament gave 9.2% to the National Democratic party of Germany (NPD), which hardly bothers even to disguise its neo-Nazi heart.

That NPD vote has now shifted almost entirely to the Alternative for Germany party (AfD), which has been able to function, though not without strain, as a home both for Tea Party-style alt-right libertarians and for people who carefully proclaim themselves to be both nationalist and socialist. The AfD’s thumping results – up to 35.5% – in parts of the old East Germany now threaten to deform the whole of German national politics. The unnerving images from Chemnitz are merely the most obvious sign of this destabilisation.

Unsurprisingly, western Germans are beginning to ask if €2tn, plus the shifting of the capital to Berlin, with all the additional spending that implies, cannot transform a place of only 17 million people, then perhaps those allegedly real and legitimate grievances are not the root of it at all. In February 2016, Die Welt declared on its front page that it wasn’t the immigrants but the Saxons who had trouble integrating with German culture.

What, then, if it’s actually a question of deep cultural differences? As soon as you look clearly at German history, you see that the vaunted north-south divide in England comes nowhere close. There were no permanent German settlements at all in what we came to call East Germany until the land was gradually conquered – it was quite literally a crusade – after AD1147. We have a very close parallel in the attempted British conquest of Ireland, which began at almost the same time. The inescapable word is colonialism and, in both cases, the vital point is that the colonisation was never wholly successful.

Look again at Hoyerswerda. It lies within the area officially recognised as the cultural homeland of the Sorbs. They are the last remnant of the Slavic natives, their language and all, and their continued presence reminds us that the whole of eastern Germany (which was much larger than now before 1945) was for 800 years contested land between Germans and Slavs.

Generation after generation, the name you called your home town – German form or Slav form – decided much of your life, just as it did and does in Derry/Londonderry. The lurking sense of an ever-present and potentially hostile Other around you permeated all of what Max Weber, father of sociology, called East Elbia. The result, just as in the slave-owning American South, French Algeria or Northern Ireland, was a political tradition in which the “poor whites” demanded (and doffed their caps to) a strong leadership of “their own”, ready to quell the native uprising if it ever came. It was this archetypally colonial politics that always made Prussia so different from the rest of Germany.

Prussia has gone. Germany no longer needs to fear itself – and no one else needs to fear it

The great tragedy of modern German, and indeed European, history is that Prussia managed to defeat and annex the whole country between 1866 and 1871 – and then systematically pushed the idea that this was “unification”. Imagine that in the mid-17th century Ulstermen and Scottish Covenanters – poorer but militarily more organised and accustomed to using armed force in daily life and politics – became paramount over the whole of a hopelessly divided Britain and then deployed all its manpower and wealth in their own interests. That is roughly what happened to the western Germans under Prussia from 1866 to 1945.

Why does it matter today? Because Germany needs to understand its own history, right now. It is hamstrung by the great national fear that militarism and authoritarianism are lying in wait for nice, liberal Germans the moment they crack down on dangers within or resist dangers without. The truth is that ruthless statism was always a Prussian thing, not a German one at all. Prussia has gone. Germany no longer needs to fear itself – and no one else needs to fear it.

Rather than let East German politics once again deform the whole country, Germany must have the confidence to use the full weight of the western Rechtsstaat – the law-based state – to make sure that we never again have to see what we saw last weekend in Chemnitz. It really is the only language these people understand.

James Hawes is the author of The Shortest History of Germany