Hitler set a bad example. He was evil. His regime was evil. His Reich was destroyed, the Nazis vanquished, the Fuhrer dying by his own hand in the ashes of the European nightmare. Bad guys lose. Good guys win. Morality, human rights, law, democracy – though with the latter, we should perhaps speak carefully – will always prevail over wickedness. That’s what the Second World War taught us.

We have grown up in a Western society that believes in such simple, dodgy, history lessons. The world’s major religions teach us about goodness, humility, family, love, faith. So why should we not – however liberal, agnostic, cynical – cling on to our fundamental belief that violence and torture and cruelty will never outlast the power and courage of the righteous?

Isis is evil. It massacres its opponents, slaughters civilians, beheads the innocent, rapes children and enslaves women. It is “apocalyptic”, according to the Americans, and therefore it is doomed. Better still, Ash Carter – the US Secretary of Defence who accused the Iraqis of running away from Isis – lectured the Iraqi Prime Minister last week. His message – I could hardly believe this naivety – was Hollywood-clear. “Civilisation always wins over barbarism.”

But does it? We only have to go back to the lie about the Second World War in my first sentence. Sure, Hitler lost. But our ally Stalin won. The 1917 Russian Revolution gave rise to one of the Gorgons of our age: Soviet dictatorship, the mass starvation leading the to death of millions, barbarism – on an Ash Carter scale – and evil incarnate ruled in Russia and Eastern Europe for more than 70 years, 40 of them after the Second World War.

The Romans kept “barbarism” at bay for almost a thousand years, but in the end the Goths, Ostrogoths and Visigoths – the Isis of their time – won. Unless you were opposed to Rome, in which case Roman barbarism – crucifixion, slavery, torture, massacre (the whole Isis gamut minus the videotapes) – was victorious for almost a thousand years.

Attila the Hun, the Scourge of God, destroyed almost everything between Persia and the Mediterranean. Ghengis Khan, an inevitable actor in this sordid drama, kept going until his death in 1227 – 30 years longer than Isis has so far ruled. His grandson Hulagu was invoked by General Angus Maude when he “liberated” Baghdad in 1917 and brought “civilisation” to Mesopotamia. Ash Carter should read Maude’s proclamation to the people of Baghdad: “Since the days of Hulagu, your citizens have been subject to the tyranny of strangers, your palaces have fallen into ruins, your gardens have sunken in desolation and your forefathers and yourselves have groaned in bondage.” Pretty much like Isis, in other words. But, by Maude’s count, this “tyranny” lasted for around 700 years.

Now let’s go forward to the years immediately after we brought “civilisation” – again – to Baghdad, by illegally invading Iraq in 2003. Between daily trips to the city mortuary and visits to tents of mourning, angry families would tell us that the “freedom” we brought had given them anarchy. They hated the dictator Saddam who slaughtered his opponents – and who imposed 24 years of “barbarism” on his people – but at least he gave them security. If you have children, these people would tell us, you want them to come home from school. You do not want them to be murdered. So which do we prefer, they asked us? Freedom or security? Democracy or Saddam?

Fearful of the Shia-dominated Iraqi government, whose militias slaughtered them, and the corrupt Arab dictatorships, who suppressed them, many hundreds of thousands of Sunni Muslims appear to have found security under Isis. Not the Shias, nor the Christians, nor the Yazidis. There is no “freedom”, as we would call it. But Sunni Iraqi men in Beirut, for example, regularly travel to and from the Isis Syrian capital Raqqa and report that – provided they don’t smoke or drink alcohol, their women are covered, and they do not oppose Isis – they are left alone: to do business, to visit families, to travel in safety. (Much the same applied under the Taliban in Afghanistan.)

ID cards are issued in Isis-land, the river police have newly-painted boats, taxes are raised, and yes, punishment is barbarous. But that does not mean the “Islamic Caliphate” is going to be conquered by “civilisation”.

And how can we believe that it will, when our own public-relations boss raves on about “British values” – and at the same time worships the venal, hypocritical, immensely wealthy and dangerous men who have helped to inspire Isis. I refer, of course, to those Saudis whose crazed Sunni Wahhabist cult has encouraged Isis, whose grotesque puritanism has led them to adopt a head-chopping extremism, which lies at the heart of Isis’s own “barbarism”. Sure, the Saudi state arrests Isis cells. But these same Saudis are now killing thousands of Shia Houthis in Yemen in a bombing campaign supported by our Western nations. And what does David Cameron do when the desiccated old king of this weird state dies? Money talks louder than “civilisation”. So he orders that British flags should be flown at half-mast. Now that’s what I call British values!

Poor old Dave. He loathes Isis but adores one of its elderly “facilitators”. Yet fear not. “Civilisation” may yet win over “barbarism”. My own suspicion is that Ash, Dave and the rest will try to buy up Isis, split them into factions and choose the “moderates” among them. Then we’ll have a new, liberal Isis – people we can do business with, the sort of chaps we can get along with, sins forgotten – and we can then establish relations with them as cosy as those the Americans maintained with Hitler’s murderous rocket scientists after “civilisation” conquered “barbarism” in the Second World War.