Since March 2011, Syria has been rocked by a revolt against the rule of President Bashar al-Assad, which has left more than 17,000 dead, according to the Syrian Observatory for Human Rights.
Here are key dates since Kofi Annan became UN-African Union envoy on Syria:
2012
MARCH 21 - The UN Security Council agrees on a statement to boost Annan's peace bid.
Annan's plan calls for a UN-supervised halt to fighting with the government pulling troops and heavy weapons out of protest cities, a daily two-hour humanitarian pause in hostilities and access to all areas affected by the fighting. It also seeks the release of people detained over the past year.
APRIL 12 - A ceasefire proposed by Annan, and agreed to by Assad's regime, theoretically comes into force.
APRIL14-21 - The UN Security Council adopts Resolutions 2042 and 2043 allowing for 300 unarmed observers to oversee the ceasefire.
MAY 25 - At least 108 dead in a massacre in the central town of Houla. UN leader Ban Ki-moon and Annan condemn the massacre. In June UN investigators say they suspect pro-government forces in many of the killings.
JUNE 6 - At least 55 people killed in a new massacre at Al-Kubeir, the Observatory says. Both the Observatory and the opposition Syrian National Council blame the massacre on militiamen loyal to Assad's regime, which denies involvement.
JUNE 26 - Fighting between government and rebels around Syrian Republican Guard bases on the outskirts of Damascus. Assad says Syria is in a "real situation of war" and says he is determined to secure victory.
JUNE 30 - Meeting in Geneva, world powers agree on a Syria transition with a unity government, before disagreement emerges on its interpretation. Washington says the accord will pave the way for the end of Assad's regime. Moscow and Beijing says it is up to Syrians to decide on their future.
JULY 6 - France host a new "Friends of Syria" meeting, but Russia and China stay away. Representatives of some 100 countries call on the UN Security Council to adopt a binding resolution imposing sanctions on Damascus.
JULY 12 - Government troops accused of killing more than 150 people in the village of Treimsa in Hama province, in what the opposition and part of the international community call a massacre.
JULY 13 - Annan says Syria had "flouted" Security Council resolutions with the Treimsa killings which UN chief Ban Ki-moon calls an "outrageous escalation."
Damascus says the army killed "many terrorists" in Treimsa, but no civilians.
JULY 15-16 - Troops battle rebels around Damascus. The International Committee of the Red Cross says Syria is in all-out civil war. Russia slams the West for using "blackmail" over a new Security Council resolution, on the eve of a meeting between President Vladimir Putin and Annan.
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