The terrorists are winning. Why pretend otherwise? The crimes of Ankara and Berlin – where families sharing festive joy were deliberately targeted and murdered – should rightly shock and appal. Such atrocities are harbingers. Millions have now watched Mevlut Mert Altıntas, an off-duty police officer who murdered Russia’s ambassador to Turkey, ranting at the camera, a slick and staged political broadcast disseminated to a mass audience. Berlin’s interior senator Andreas Geisel strikes a defiant note. “This is a horrific event,” he says. “But it won’t change the way we live life here in Berlin.” Berlin will indeed prove more resilient to this kind of atrocity than many European cities, but we are deluding ourselves if we pretend terrorism has not already dramatically changed our way of life.

Islamist terrorist fanatics and the west’s ascendant populist right are now working in tandem. They are feeding off each other. They are interdependent. Their fortunes rise with each other. This morning Nigel Farage tweeted: “Terrible news from Berlin but no surprise. Events like these will be the Merkel legacy.” What kind of contemptible individual mixes horror with vindication? From Donald Trump to France’s Marine Le Pen to the Netherlands’ Geert Wilders, the populist right will now be carefully plotting how they will extract political dividends from the horror. Muslims as a whole will fall under ever greater suspicion.

That is, of course, exactly what the fanatics want. Don’t listen to me: heed the words of Nicolas Hénin, a Frenchman who survived being taken hostage by Isis. After the Bataclan atrocity, he wrote that his captors would be scanning social media and celebrating: “‘We are winning’, they’d say. They will be heartened by every sign of overreaction, of division, of fear, of racism, of xenophobia; they will be drawn to any examples of ugliness on social media.” What he wrote is so depressingly, glaringly obvious to anyone who ponders it for more than a moment: and yet still the script written by the fanatics will be followed to the letter.

Yes, lessons need to be learned. Turkey’s besieged opposition HDP party – in a country rapidly degenerating into dictatorship – “harshly condemn” the ambassador’s murder. They also say this murder demonstrates that “Turkey is unfortunately no longer a secure country due to recent domestic and international policies”. Turkey’s regime has backed fundamentalist rebels who hijacked what began as a Syrian cry for freedom. We do not yet know exactly what drove Altıntas to commit his crime: but look at how the western media accept that foreign policy could be a factor, noting as they do that his expressed motive was vengeance for Aleppo and Syria. As journalist Mehdi Hasan puts it: “Western pundits are happy to link terror attacks with Russian foreign policy, but never with western foreign policy.”

Here is the danger of what now beckons. More Islamist terrorist attacks will come. The populist xenophobic right will continue to surge, and it will capitalise on the atrocities. Hatred against Muslims – and demands for collective punishment – will grow. Civil liberties will be rolled back. Those on the left who oppose racism and support compassion for refugees will increasingly be regarded as the enemy within. Democracy will be chipped away. The west will continue its inexorable decline, not because of the threat of “Islamisation”, but partly because of political consequences arising from the fear of Muslims and foreigners. Picture how Donald Trump will respond after the first major terrorist attack. If, in a century’s time, historians ask why the west fell into a spiral of decline, the answer will not be that we were overrun by fanatics, but that we succumbed to their wishes.

It doesn’t have to be like this, no. But unless reason and common sense trump hatred, 2016 will mark the beginning of a new, dark era.