The Syrian civil war, which grew out of an uprising against Assad, has killed more than 250,000 people since March 2011. About half the country's prewar population of 23 million has been displaced, including more than 4 million who have fled Syria to other countries in the Middle East and Europe. Tactics such as encircling populated areas have caused untold cases of starvation, malnutrition and chronic illness. The U.N. refugee agency says Syria is the leading source of refugees, pushing Afghanistan — which had held that status for more than 30 years — down to second place.
The war has defied all attempts for a diplomatic solution. Unimaginable suffering has unfolded while the world stands witness. The emergence and spread of the violent Islamic State group as the most potent opposition to Assad has led to renewed diplomatic activity to try and end the war. (AP/Reuters)