As Syrian tanks prepared to advance on Jisr al-Shugour late last week, Robert Gates, the US defence secretary, launched an offensive of his own. In a speech in Brussels, he dismissed most of America’s European allies as a useless bunch of timewasters. I paraphrase – but not much.

Mr Gates pointed out that while all Nato countries had voted to intervene in Libya, most had chosen not to participate in the actual fighting. Even those European countries that are taking part began to run short of munitions, just 11 weeks into the fighting – forcing an exasperated America to step into the breach. More broadly, a situation in which the US accounts for 75 per cent of the military spending in Nato was “unacceptable” and unsustainable. If it is not rectified, Mr Gates predicted, Nato faces a “dismal” future.

The conjunction of the Gates speech and the Syrian civil war is very telling. It explains why a 20-year experiment with the idea that western military force can put the world to rights is coming to a close.