FILE - In this Friday, March 18, 2011, file photo, wounded anti-government protesters lie on the ground as they receive medical help at a field hospital during clashes with security forces in Sanaa, Yemen. Ten years ago, an uprising in Tunisia opened the way for a wave of popular revolts against authoritarian rulers across the Middle East known as the Arab Spring. For a brief window as leaders fell, it seemed the move toward greater democracy was irreversible. Instead, the region saw its most destructive decade of the modern era. Syria, Yemen, Libya and Iraq have been torn apart by wars, displacement and humanitarian crisis. (AP Photo/Muhammed Muheisen, File)