If you want to know why the Syria conflict can’t be ended by willpower or the snap of a fingers, this is a good analysis by Gareth Porter. The latest peace talks don’t include any significant armed combatant party in Syria – not any stripe of rebels, not the government, and certainly not ISIS. Practically speaking, on the side of the anti-regime forces, there is nobody that the rest of the world is comfortable negotiating with who could actually control any armed fighters if a deal was reached. The Syrian government (or even just the Army) doesn’t want to negotiate a deal either because they have no interest in signing a deal that brings al Qaeda/Nusra to power, and they are currently the primary non-ISIS opponent.
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Flag of the Syrian government.