The biggest powers in the world were not able to find a way to stop the war in Syria when it broke out in 2011.
More than four years on, a whole new set of challenges is coming from Syria, and other countries in the Middle East and Africa. And the world's biggest powers are struggling once again to find answers that work.
The new crisis is about refugees. The European Union is discovering, belatedly, that it is impossible to avoid the consequences of a range of wars and civil conflicts right next door.
Some Western politicians, and journalists, are taking proper notice for the first time of a refugee crisis that has been a huge concern for Syria's neighbours since the war started.
The difference now is that refugees, in big and increasing numbers, are trying to get to the richest countries in Europe.
The EU is discovering that the Mediterranean is an inadequate moat. Eventually a response will be found to handle this summer's refugees.
Yarmouk example
But the fundamental reason why they will continue to come is still there.
And that is war in Syria, in Libya, in Iraq and Yemen. Violence, instability and chaos make lives miserable, dangerous and short across a broad swathe of the Middle East and Africa. It is not surprising that people want to get out.
Some may not have their lives threatened directly, but they want to leave before the worst happens.
People do not leave their homes lightly. They flee, and sometimes take dreadful risks at the hands of people smugglers, because the alternatives are so much worse.
I walked through the ruins of Yarmouk, one of the most fiercely contested battlegrounds in Damascus, only a few miles from the centre of the city.
Yarmouk used to be a Palestinian refugee camp for families who had fled or been driven from their homes when Israel won its independence war in 1948.
Over the last three years in Damascus I have spent nights watching Yarmouk being pounded. On the day I was there, it was quiet and eerie.
The Syrian army and Palestinian fighting groups control roughly half of Yarmouk. All the civilians who lived there have gone. Some are in shelters nearby. Some are trying to get to Europe.
Street after street was in ruins. Every building was damaged, not just by artillery but by thousands of rounds that were fired in street fighting.
