The German defence ministry set out its worst-case scenario for the year 2040 in a secret document that was leaked to Der Spiegel last week: “EU enlargement has been largely abandoned, and more states have left the community … the increasingly disorderly, sometimes chaotic and conflict-prone, world has dramatically changed the security environment.”

The 120-page-long paper, entitled Strategic Perspective 2040, is a federal government policy document – and the scenarios it imagines are grimly realistic: an east-west conflict in which some EU states join the Russian side or a “multipolar” Europe, where some states adopt the Russian economic and political model in defiance of the Lisbon treaty.

That the document exists at all is a sign of the increased tension in the global system. The German military’s tradition of rigorous logistical planning for every eventuality began with the celebrated German field marshal Moltke in the 1850s and has three times paid off with initial success: in 1871 against France, in 1914 and 1939 against the rest of Europe. In the post-cold war era, as Der Spiegel puts it, allowing German generals to make statements about the future was “too risky”. That changed with Russia’s annexation of Crimea in 2014.

Despite the alarmist headlines it has generated, the leaked document is, if anything, overoptimistic. In three out of the six scenarios, things go so well that Europe resembles the Biedermeier era – 1815-1848 – of domestic bliss and military boredom. Its negative scenarios – which see the US struggling to avoid isolationism and China locked in a cultural war with the west – were written before Donald Trump came to power and before Xi Jinping’s strategy of creating a politicised Chinese infrastructure across Asia.

The journalists to whom the document was leaked have omitted any details of what Germany is planning to do about the EU’s possible collapse and fragmentation. But this is the problem facing the entire western world.

Though the urgent problem is terrorism, the important ones are the decline of consent among populations for the present economic system and high levels of migration. They have begun tearing holes in the fabric of the EU itself – via the Greek crisis of 2015, Brexit and in the standoff between the Polish and Hungarian governments and the European commission.

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Right now, the issue at the front and centre of German political minds is the French president Emmanuel Macron’s proposal for accelerating Europe’s economic integration, which almost everybody in Germany wants to reject – Angela Merkel’s CDU/CSU because it implies requiring more fiscal transfers to poor countries in the periphery; the Social Democrats because it will weaken the remaining social protections for workers; the far-right AfD because it means more Europe. Every conversation I have had with German politicians and activists since the country’s election has revolved around fears that the million-plus recent refugees will not be properly integrated, and that tolerance for further social change among older, less-educated Germans is at breaking point.

After Brexit has happened, the mature democracies of Europe should be pushing to consolidate their project, telling a coherent, positive story to their increasingly critical electorates. Yet they cannot – because the only coherent story Europe has is more globalism and more market, and that is what the populations are rejecting. Meanwhile, Russia and China are no longer nibbling at the edges. They have begun to gnaw. A new “great game” is being played in the eastern Mediterranean in particular and “the west” barely has a strategy.

This weekend evidence emerged that indicted former Trump adviser George Papadopoulos had made a visit to Athens coinciding with the visit of President Putin. There is no evidence that they met, but they did not need to. Papadopoulos’s interlocutor in the Greek government is the defence minister Panos Kammenos, who heads a small nationalist party in the Syriza-led coalition and is one of the most pro-Kremlin politicians in any Nato government.

Now, after the EU ordered the mass privatisation of Greek assets, Chinese money has surged in, buying the whole container port of Piraeus and in August signing billions of euros worth of investment deals with Greece. As Costas Douzinas, the Syriza MP who heads the Greek parliament’s defence committee, put it: “While the Europeans are acting towards Greece like medieval leeches, the Chinese keep bringing money.”

If the Germans are making contingency plans for the collapse of Europe and the breakup of the global order then, presumably, someone at the UK’s Defence Academy in Shrivenham is doing the same. It would be better, though, if politicians started engaging the British electorate in a sober and non-partisan appraisal of the problem we face.

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Putin’s Russia is waging hybrid warfare against western democracies; not just through cyber-attacks or the placing of millions of pounds worth of ads for fake news on Facebook. It is also funding rightwing populist parties and using media influence to revel in the sleaze, corruption and sclerosis in European democracies. In turn, there is a tendency among centrist politicians to say that all opposition to the status quo – most recently in the Catalan referendum – is Kremlin-inspired.

The assumption behind the UK’s repeated promise of security cooperation with Europe after Brexit is that the core democracies – Germany, France, Italy and Spain – will remain committed to Nato, democracy and the rule of law. And that a reformed and revitalised Europe will deliver enough jobs and growth to sap the energy of the nationalist and xenophobic right. But it would also be wise for politicians to begin admitting that these things are no longer certain. If we want order, we have to create it – through engagement, multilateralism, by accommodating what we can of the demands of rising powers and through the promotion of resilient democratic institutions. If we fail to achieve order, we must deal with disorder when the US is no longer a reliable ally, nor even a stable democracy.

Britain’s new defence secretary should have a long look at the leaked German document. It will make sober reading alongside the defence spending cuts he is being told to make.

• Paul Mason is a Guardian columnist