So for the time being the shaky centre of Europe is holding. Barack Obama and Vladimir Putin are at least talking, while the Ukrainian president Petro Poroshenko continues to show admirable restraint. But listen closely and it is hard not to hear the echoes of history in Europe’s collective failure to confront naked Russian aggression.

For weeks now, the US - supported by Britain, to the irritation of many European allies - has been demanding tougher sanctions against Moscow, warning of what might happen if nothing was done to stop Putin giving heavy weapons to separatist rebels in eastern Ukraine. But as so often in the past, a timid and divided European leadership demurred. They agreed to a feeble set of sanctions on Wednesday, only to have their folly exposed for all the world to see a day later: a Malaysian Airlines jet plummeting to earth, caught in the crossfire of a conflict that Europe should have done more to prevent, at a cost of 298 innocent lives.

No one should doubt that the blame for this tragedy lies squarely at the feet of Mr Putin - even as he was promising a ‘‘peaceful outcome’’ to Angela Merkel, a convoy of cast-off tanks and armoured cars was being sent into the rebel strongholds. But Europe’s half-hearted response and the weakness of the West in general also played its part.

As before World War I, the centenary of which falls next month, there is a detectable sense of complacency among the coddled citizens of Europe and America. Perhaps it is understandable. We have never been more comfortable, the internet quite literally lets us swoop across the world, plucking its fruits at whim. Life for many millions is good; across the developed world, violent crime is falling, the recession receding, we are living longer and have choices galore. With Afghanistan and Iraq behind us, war is now something that takes place in far-off lands.

But the belief that economic inter-dependence would protect us from wars - that the cost of conflict would far outweigh the gain - is a fallacy. Norman Angell, a leading pundit of his day made that argument back in 1910 in his book The Great Illusion. But he overlooked the fact that nationalist ambition is often irrational, as Mr Putin has shown by continuing to prosecute his proxy war in Ukraine despite his economy being on the brink of recession.