Children on outskirts of Damascus
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The child victims of Syria's four-year long conflict

Almost four years after what began as peaceful protests, half the population is still displaced, large areas of the country lie in ruin, and President Assad is still firmly in power.

The crisis facing Syria has been called "the biggest humanitarian test of the 21st century".

BBC Middle East Editor Jeremy Bowen reports from Damascus on why Syria's war is so hard to stop.

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