Peter Franklin is an Associate Editor of UnHerd.

Are we on the brink of a much wider European war? It’s still too soon to tell, but there’s one parallel with 1939 that already holds up: the failure of appeasement. We tolerated Russia’s annexation of Crimea and the Donbas. We kept Ukraine at arm’s length from NATO and EU membership. We negotiated with Putin in good faith. He invaded anyway.

There is an isolationist element with the conservative movement — especially in America — that urges us not to get involved. According to Tucker Carlson, the Fox News host, Russia “has no intention of invading Western Europe” and that “Vladimir Putin does not want Belgium…” Well, not even the Belgians want Belgium, but what about the rest of the continent between Lviv and Brussels? Doesn’t that matter?

If Putin prevails in Ukraine, why should he stop there? He’s got the remainder of the former USSR left to reconquer — or, somewhat further afield, the old Russian Empire. If Kyiv is fair game, then why not Vilnius, Warsaw or Helsinki? Margaret Thatcher once said that “the problem with socialism is that you eventually run out of other people’s money.” One might add that the problem with isolationism is that you eventually run out of other people’s countries.

And yet I can understand where the isolationists are coming from. After the foreign policy failures of the last two decades, a backlash was inevitable. Twenty years ago, the Republicans were the party of George W Bush. Under the influence of the neocons, they pursued an interventionist agenda all the way into Iraq. It was a bloody disaster. Furthermore, the pursuit of regime change by means of military invasion provided Putin with the precedent he’s cynically exploiting today.

And so we find ourselves standing among the ruins of not one but two foreign policy paradigms — isolation and intervention. We desperately need an alternative to both. But if we can neither ignore our enemies nor compel them to change their ways, what can we do? The answer is that we must look inwards and change ourselves.

We’ve learned the hard way that western democracy is not the irresistible force that the interventionists imagined it to be. But that being the case, we should strive to make it an immovable object — a fortress of freedom that will not crack no matter what our enemies throw at it.

For a historical parallel we should to look to the fifth Century and the fall of Roman Empire. Or, rather, to the fall of the western Roman Empire. Crucially, the eastern half — centred upon Constantinople — did not fall. Indeed, it survived and flourished to become what we call the Byzantine Empire.

Why did the Byzantines (who called themselves Romans) endure while their western brethren crumbled? Some say it all comes down to geography. According to this theory, the west was wide open to barbarian invasion while the east was protected by mountains, deserts and seas. But that’s only partly true. Outlying western areas like Britannia and Gaul were indeed vulnerable — but Italy was eminently defensible, protected by the Alps and the Mediterranean. And, besides, Constantinople came under repeated attack and yet stood for more than a thousand years.

What really made the difference was leadership. After the empire was permanently divided between eastern and western emperors in 395, the east had the benefit of competent, visionary leaders committed to the long-term survival of the realm, while the west — with fleeting exceptions — did not.

So what can we learn from the eastern emperors of the fifth century? Let’s start with Theodosius II (402-450) — the builder of the formidable Theodosian walls. Constantinople was originally chosen for its strategic position. Commanding the Bosporus, the city was surrounded on three sides by the sea — and guarded by the Byzantine navy. That just left the fourth side open to attack by land. Theodosius was dissatisfied with the city’s existing defences and so he ordered a massive upgrade.

The eventual result was a double wall and moat, three-and-a-half miles long. Time-and-again Constantinople withstood assault from its enemies; but just as important were all the times that would-be attackers decided not to bother because the defences were just too strong. Contrary to the twitterings of a certain ice cream manufacturer, the lesson of history is that you can simultaneously prevent and prepare for war.

Another Byzantine emperor who should inspire us is Anastasius I (491-518). He too was a wall builder, but even more important were his financial reforms. In previous centuries, the rulers of Rome had allowed the currency to become debauched. Much of the empire’s economic activity — including tax collection — reverted to payments-in-kind. Needless to say, this was ruinously inefficient.

Anastasius restored confidence in the currency — and not just the gold coinage used by the rich, but also the copper coinage used by ordinary people. At the same time, he reined in wasteful spending and improved the management of the imperial estates so that the most onerous taxes could be cut. However, he didn’t pursue the false economy of cutting back on essential infrastructure and maintenance.

Anastasius — a pious career civil servant — may not have been the most exciting of emperors, but he taught us that, in matters of civilisational endurance, solvency is next to potency. Something for our wasteful governments and tax-dodging corporations to contemplate.

The final emperor I’m going to mention is Leo I (457 to 474). In the fifth century, the barbarians weren’t just at the gate,  but also inside it. As part of its decline, Rome had gone from fighting Germanic invaders, to bribing them to go away, to paying them to man its armies. Eventually, barbarian generals like Stilicho and Ricimer became the most powerful men in the western empire. The final western emperors became their puppets — until Odoacer called an end to the farce and deposed the last emperor, Romulus Augustulus, in 476.

Meanwhile in the east, barbarian generals like Aspar were almost as powerful as their western counterparts. But when he became emperor, Leo refused to be a puppet. He out-manouevred Aspar, had him executed and began the process by which the Byzantines took back control. They had realised that any state that depends on hostile foreigners for its security is ultimately doomed.

Today, we are fortunate that the military security of the West is still in western hands. However, the same cannot be said for our energy security. The various sanctions announced since the invasion may go further than most people (including Putin) anticipated, but crucially they don’t include an embargo on Russian oil and gas exports. While Russian tanks roll across Ukraine, we continue to fill the Kremlin’s coffers.

And it’s not just Russian fossil fuels we’re addicted to. Decades of thoughtless globalisation have left the West deep in debt, dependent on vulnerable supply chains and contemptuous of our own civilisation.

This is not sustainable. The invasion of Ukraine is not the last crisis that we will face this century. In a dangerous, multipolar world we will be tested many times. We can prepare to face the barbarians or merely wait for them. But, either way, they’re coming.