We live, 20 years after the murder of an estimated 800,000 people, in the shadow of Rwanda. And this weekend, on the anniversary of the start of the Rwanda genocide, is a good time to contemplate the significance of that shadow.
A tiny country, in the middle of Africa, less than one tenth the size of the UK: how come Rwanda forced the rewriting of the rules of international behaviour?
One word sums it up: shame. Shame that the peoples of the rich world stood by, saw what was happening, and did nothing to stop the slaughter. And out of that shame grew a new doctrine, solemnly endorsed by the United Nations. It became known as the responsibility to protect (R2P in diplo-speak), and it was drawn up, in the words of the International Coalition for the Responsibility to Protect, "to address the international community's failure to prevent and stop genocides, war crimes, ethnic cleansing and crimes against humanity".
Quite right, too. In Kosovo, and then in Sierra Leone, international military action did stop the brutal slaughter of civilians. Tony Blair made a speech in Chicago in April 1999 in which he unveiled what he called his "doctrine of international community".
In it, he said: "We are all internationalists now, whether we like it or not. We cannot refuse to participate in global markets if we want to prosper. We cannot ignore new political ideas in other counties if we want to innovate. We cannot turn our backs on conflicts and the violation of human rights within other countries if we want still to be secure."
But then came the US-led invasions of Afghanistan following the 9/11 attacks in 2001, and of Iraq in 2003. Neither, despite what might have been claimed at the time, was in any sense a humanitarian intervention; and both turned into grim, messy military occupations. It didn't take long for voters to lose faith in the notion that military interventions in far-away places might help to make the world a better place.
Nowhere does Rwanda cast a longer shadow than in Syria. War crimes and crimes against humanity aplenty, an estimated 150,000 people killed, yet no protection on offer from foreign powers. Why? Because of Afghanistan and Iraq. Because memories of losses there, both military and civilian, are far fresher than memories of the horrors of Rwanda.
This is not an argument for sending in foreign troops to Syria. To do so, in my judgement, would make an appalling conflict even worse. But surely we need to ask ourselves this weekend, as we are reminded of how we failed the people of Rwanda 20 years ago, if we are failing the people of Syria today.
And while I'm on the subject of failing to live up to our solemnly-proclaimed "responsibility to protect", how about the people of the Central African Republic, far closer to Rwanda than Syria is? It's estimated that up to a million people there have had to flee from their homes -- most of them Muslims, terrified of Christian militias who have embarked on a sectarian cleansing campaign of brutal ferocity.
At a summit meeting of EU and African leaders in Brussels this week, the UN secretary-general Ban Ki-Moon warned that the violence in the Central African Republic could soon turn into genocide. That word again. The shadow of Rwanda again.
There are already some 8,000 African and French troops in the country, but I have yet to detect any sense of urgency - responsibility, if you prefer - to protect the hundreds of thousands of people who have fled in fear of their lives.
Yes, I know. We can't save everyone. We're broke, and military expeditions are hugely expensive. But that's not really it, is it? We've lost the will, as well as the means.
But here's the thing about shadows. You can turn your back on them, but even if you ignore them, they're still there. You can't get rid of them. That's why I say we are still living in the shadow of Rwanda.