If Russia and Iran withdrew their support from Damascus, Mr Assad would not survive the month

The Pope has called the recent use of chemical weapons in Idlib province, Syria, “an unacceptable massacre”.

As the details emerge, reminding us of not just the horror of chemical weapons but also the ruthlessness of governments who are prepared to use them, these words of the Pope and others around the world beg the following question: “Just what are the world’s authorities going to do about it?”

Donald Trump has answered that question. He also condemned the attack, and America has already taken military action. Indeed, if America had acted the last time a “red line” was crossed, perhaps we would not be where we are today. Perhaps, just perhaps, that might have precipitated the collapse of the Assad regime, or at least stopped the regime using chemical weapons again.

But as it turned out, the Obama administration did not intervene, Mr Assad was given a de facto license to continue, and continue he did. Having failed to take a stand then, the Americans have taken a stand now, when doing so has become much harder, at least from a political perspective. (No one can blame them for intervening in Syria now from a moral perspective, as Mr Assad and his enablers have put themselves beyond the pale.) The phrase “surgical strikes” sounds plausible in a television studio but such strikes may well lead to other operations, and there is always the danger of conflict with Turkey, Iran and above all Russia. And what follows now? There is no acceptable alternative government to Mr Assad’s waiting in the wings.

It is quite possible that the current American intervention may in the end make little difference beyond signalling the American government’s disapproval with Tomahawk cruise missiles rather than just with words. The problem of Syria seems intractable.

The road to peace in Syria is effectively blocked in Teheran and Moscow. As long as these backers support Mr Assad, then he will hang on to power. After all, his physical grip on the country (or the bit of it he still controls) depends on Russian power in the air and Iranian and Hizbollah fighters on the ground. Were these to be withdrawn, Assad would fall, as his own army simply does not have the manpower to occupy the country.

If one is looking for a historical parallel – something I always like to do – one should look to the Kingdom of Naples in its final period from 1848-1861. The Bourbon monarchy collapsed because it was abandoned by the great powers of Europe (apart from the Russians, who were too far away to help practically), and crucially no longer propped up by the Austrian troops who had acted as an occupying power after the suppression of the revolts of 1848.

If Russia and Iran withdrew their support from Damascus, which means effectively if the current rulers of Russia and Iran were overthrown, then Mr Assad would not survive the month. This means, effectively, the best hope of the Syrians depends on the Russian opposition and the Iranian opposition.

Just recently Russia has seen its largest street protests for some time. Mr Putin knows that other authoritarian regimes in Europe have been brought down by street protests, and is taking no chances, as the wave of arrests and imprisonment of protestors has shown. It takes guts to protest in Russia.

For the people of Idlib, these protests may prove to be the seeds of hope, and in the end be of more use than Tomahawk cruise missiles or the words of condemnation from the Pope and other leaders.