The conflict has spawned Isis.
It's destabilised an already volatile Middle East, and has cost the big humanitarian agencies like the world food programme, billions and billions of dollars.
The great danger, though, are the millions of children now growing up without any form of education.
Syria, with its once brilliant universities is, as we know, a pile of rubble.
Before the conflict, 97 per cent of Syrian children had access to education.
The government there pledged to eliminate illiteracy by 1991 and so schooling become compulsory, even in some of the more remote desert areas. And before the conflict, literacy rates were thought to be over 90 per cent.
Now, millions of children have been without access to education for six years.
Desperate parents have married some off - as children. They simply can't support them any more.
Others are working in the fields. You see them when you travel through the Bekaa Valley, which divides Lebanon and Syria.
Tiny children dig potatoes or tend tomatoes, most for a few cents a day.
But the real issue is when displaced boys don't have access to education.
Instead of finding camaraderie and mentors in a school environment, they look to armed groups or soldiers as their heroes.
They're given a gun, they join a group, and in exchange for food, shelter and money, they fight.
Education stops that. Education offers social stability, a form of protection for children, and in time it will help fuel - you would hope - Syria's economic recovery.
It's such a challenging situation. The scale of the crisis of huge. You're talking about millions of people.
But without education, the conflict will continue. And yet how do you provide education to millions of children?
It's hard to grasp on this side of the world, isn't it?
But every year, when I mark the anniversary of the Syrian conflict, I always hope that I won't have to mark it the following year and that the conflict will be over. But here I am marking it again for a sixth year.
Education, in whatever capacity, surely has to become a major priority for not just the humanitarian agencies, but for the super powers, and the UN too.
The long-term cost of not educating Syria's children is simply too great.