Garvan Walshe is a former National and International Security Policy Adviser to the Conservative Party. He is CEO of Brexit Analytica.

Nominative determinism has its limits. Asking Russia, whose planes helped Assad reconquer Aleppo, “Are you truly incapable of shame?”, Samantha Power, author of the fine A problem from Hell: America and the Age of Genocide, confirmed she had no power herself. Abandoned by her boss, who blocked air strikes against the Syrian regime in 2013, and his successor indifferent to anything but his own ego, she was left asking rhetorical questions to the Security Council, as though she represented Papua New Guniea or Luxembourg, not the United States of America.

It was no different in the House of Commons where supporters of intervention back in 2013 gathered to condemn the absent majority who had blocked it. It was George Osborne who reflected on the terrible effects of that vote:

“We did not intervene in Syria, and tens of thousands of people have been killed as a result while millions of refugees have been sent from their homes across the world. We have allowed a terrorist state to emerge in the form of ISIS, which we are now trying to defeat. Key allies such as Lebanon and Jordan are destabilised, and the refugee crisis has transformed the politics of Europe, allowing fascism to rise in eastern Europe and creating extremist parties in western Europe. For the first time since Henry Kissinger kicked it out of the middle east in the 1970s, Russia is back as the decisive player in that region. That is the price of not intervening.”

The consensus in the chamber revolved around humanitarian aid, because – unwilling to protect them from their killers, or offer them sanctuary here instead -that’s all we have left. Opponents of intervention, except where they held office on the SNP and Labour front benches, stayed away. England spectates, while Assad’s goons do their duty.

We do nothing because the political incentives push towards abandoning the international system instead of reinforcing it. Baby boomers and millennials for opposite reasons together fix our politics against intervention.

The boomers are terrified by the depth of globalisation. They think it’s destroyed jobs and their culture, leaving them in a world that no longer makes sense to people who came of age when the large nation state was still an economic unit as well as a source of political identity. At this same it time attacks their culture as people speaking foreign languages, wearing foreign clothes and preaching foreign religions come here in large numbers. It is not that Syria is a far away country of which we know nothing. It is far too close, and we think we know too much about it. Why should we send our boys to die for their people?

The young think globalisation has gone further than it actually has: that because all cultures could be equivalent, they should be treated as such by default, and to even ask questions about female genital mutilation, or the large number of terrorists who claim to be inspired by Islam, is to fall prey to racist ideas. What position, they ask, are we in to talk about civilian casualties when we caused so many ourselves?

They’re so eager to learn from the world that they can’t imagine we still have something to teach it too, and that when it comes to political organisation, or the rule of law or human rights, the system invented in the West is still the best place to start from. It’s the system Syrians began demonstrating peacefully for in 2012. Millennials won’t face up to the fact that they’re dying now because we were insufficiently proud of our system to kill to protect people who wanted to adopt it.

Now the whole system is under threat. The international order that secures the global trade that keeps our economies going and allows us to spend just two per cent of our income on defence is only as strong as its opponents think it is. The next US president hates the very concept, and Congress will have its work cut out protecting it from him. Britain will be distracted for a decade by Brexit. France might fall to Le Pen. The coming generation needs to learn that our system isn’t natural, and its rules are not self-enforcing. It was built in the 1940s and 1950s by people who’d seen what happens when it is allowed to rot because nobody wants to get their hands dirty to defend it.

If we do not, the historians of 2050 (should there be any left) will record how Syria, like Abyssinia in the 1930s, marked the point at which the international system’s decay became irreversible and the irreparable slide towards general war began.