A rebel fighter takes aim during a training session in Eastern al-Ghouta, a rebel-held region outside the capital Damascus, earlier this month. Russia is inviting Syrian opposition groups to peace talks in Moscow, but few of them want to go to a country that supports Syrian President Bashar al-Assad. Abd Doumany/AFP/Getty Images hide caption

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Carla del Ponte, a diplomat and prosecutor who now serves on the Independent International Commission of Inquiry for Syria. Salvatore Di Nolfi /EPA /LANDOV hide caption

toggle caption Salvatore Di Nolfi /EPA /LANDOV