But despite pledges by the government and opposition to implement the plan, a cease-fire never happened, and fighting continued to escalate to a point where the conflict was recently declared a civil war. For many diplomats and military experts, Annan's plan is all but dead.
If Assad were to fall, it's unclear whether the major powers could unite again at a Bonn-style summit to set a roadmap for Syria.
For the United Nations, which deals with the governments of its 193 member states, the immediate question if Assad fell would be who -- or what political group -- replaces him.
In the case of Syria, there is a divided opposition outside the country and disparate groups of young fighters inside the country, some aligned to the Free Syrian Army.
