It was an unusual document Angela Merkel just found in her in-tray. Written in French and on joint letterhead, 15 members of France’s Parliament penned an open letter to the German Chancellor.

The French politicians are from both chambers of the house, from parties across the political spectrum but from one region: Alsace. And that is enough to unite them in their concerns about Germany’s behaviour in the Covid-19 crisis.

As the largest country in the European Union, Germany always had to balance its role. On the one hand, its sheer size gives it responsibility and often demands leadership. On the other hand, this size can easily make any such attempts look like threats or bullying.

However, no matter the size, there are also basic rules of good behaviour that no country should ever ignore. That is what so upset the French parliamentarians. And that is an issue that goes well beyond Alsace or France.

Like many other countries, Germany closed its borders at the beginning of the Covid-19 crisis. And just like these other countries, Germany also allowed exceptions for cross-border commuters. Except the Germans are doing their best to make life miserable for French citizens working on the other side of the river Rhine.

“Far be it from us Alsatian parliamentarians to pass a value judgment on the management of the health crisis by the German authorities,” the French MPs write. “But allow us nevertheless to make you aware of the anger of the citizens of Alsace at the consequences of the decisions that have been taken.”

The frustrations, as one of the MPs later also explained to the German media, were an open hostility to French commuters. There was even the case of a French accountant working for a German company who was recently denounced in a bakery shop for wanting to buy bread for her lunch break. The summoned police officers instructed her that French people are not allowed to buy food in Germany. She also had to pay a fine for the offence.

“What has become of the Treaty of Aachen? What became of the Franco-German Friendship? What becomes of Europe?” the letter-writers ask the German Chancellor.

These are good questions, not just in this public health crisis. Once again, Covid-19 has accelerated and made more visible what had been brewing under the surface for a long time. In this case: the fracturing of the once-dominant axis between Paris and Berlin.

For decades, French Presidents and German Chancellors pushed European unity forward. They were not always in complete agreement. In fact, their differences in policy views are legendary. But in the end, when it mattered, they always pulled together. Charles de Gaulle and Konrad Adenauer did that. Valéry Giscard d’Estaing and Helmut Schmidt did the same. As did François Mitterrand and Helmut Kohl.

That Franco-German axis has deteriorated markedly over the past two decades. It reached a new low in the relationship between Emmanuel Macron and Angela Merkel. Three years ago, the French President gave a speech at the Sorbonne university in which he outlined his vision for a more united European Union.

At the time, Macron had only just been elected months before, so it was a bold new initiative. It was designed to restart the European project after many years of dealing with the European debt and monetary crisis.

Yet the answer Macron got from Berlin was nothing, nichts, rien. Not that the German government would have openly disagreed with the French President (which it probably did in private). It was worse, the Merkel government did not even acknowledge Macron’s ideas. There was silence from Berlin.

Eventually, after many months of waiting, Merkel’s hapless successor as chair of the governing CDU party, Annegret Kramp-Karrenbauer, provided some sort of a reaction. But it was no major speech, just an op-ed in a Sunday newspaper. It did not come from Merkel but from a politician who, at the time, did not even hold a government office. Oh, and of course Kramp-Karrenbauer did not agree with the French President’s proposals.

It does not require great imagination to figure out how the French side would have regarded the German engagement. Indeed, the frostiness in the bilateral relations has been palpable for years.

It is this context in which Covid-19 has exacerbated the damage and advanced the alienation between France and Germany. At least before the crisis, the French saw themselves more or less at eye-level with their Eastern neighbours. Not anymore.

Writing in the Le Figaro newspaper, the essayist and lawyer Nicolas Baverez recently explained what damage the crisis had done to France’s position in Europe. “The crisis is widening the gaps between nations, particularly in Europe and the euro zone,” Baverez wrote. “France entered the epidemic as an intermediary country between Northern and Southern Europe; it will emerge as a Southern country, whose sovereignty will be alienated and handed over to Northern European countries and financial markets.”

From Germany’s perspective, it would have been wise not just to fight the virus but also to keep in mind the sensitivities of its European partners.

Instead, in this crisis Germany’s view is inward-looking. Germany does what it thinks it must do for public health – without consideration for losses and, of course, without consideration for its neighbours.

From the perspective of the other European countries, Germany acts like a bulldozer. From its own perspective, Germany does not even notice it.

Yes, it is also true that Germany provides intensive medical care for Covid-19 patients from other EU countries like France and Italy. But such assistance is simply not noticed in the face of Berlin’s fiscal indifference to their plight.

If French commuters are then denounced for buying bread in a German bakery, then this really is just the last straw.

To make matters worse, when protective masks are delivered to France from China, of all countries, it underpins two things. That France has become a recipient of aid, and that this aid does not come from its once allied and friendly neighbour.

If at some point this crisis is no longer acute, then the Franco-German axis will feature only in history books – and the EU will not be able to find a replacement for it anytime soon.