In 2011, as regimes crumble across the region, tens of thousands of Syrians take to the streets to protest against corruption, high unemployment and soaring food prices. The Syrian government responds with live ammunition, claiming some 400 lives by May.

At the urging of Western countries, the UN Security Council condemns the violent crackdown. The EU and US implement an arms embargo, visa bans and asset freezes in the months that follow. With the backing of the Arab League, calls eventually grow for the Syrian president's departure. But not all UN members agree with this demand.

Bashar al-Assad - who has been in power since the death of his father in 2000 - sees his reputation wane with the continuing unrest. He refuses to end decades-long emergency rule, which allows for surveillance and interrogation. Russia backs its ally, supplying weapons and vetoing UN resolutions on Syria multiple times.

By the end of the year, human rights groups and the UN have evidence of human rights abuses. Civilians and military deserters are slowly beginning to organize themselves to fight back against government forces, which have been targeting dissidents. More than 5,000 have died so far in the fighting. It will take another six months before the UN acknowledges that a war is taking place on Syrian soil.

In September 2012, Iran confirms that it has fighters on the ground in Syria - a fact long denied by Damascus. The presence of allied troops underscores the hesitance of the US and other Western powers to intervene in the conflict. The US, stung by failed interventions in Afghanistan and Iraq, sees dialogue as the only reasonable solution.

As the death toll nears 100,000, the number of refugees in neighboring countries - such as Turkey and Jordan - hits one million. That number will double by September 2013. The West and the Arab League have seen all attempts at a transitional government fail in the two years of war, watching as fighting spills over into Turkey and Lebanon. They fear Assad will stay in power by any means possible.

Assad has long claimed he's combatting terrorists. But it's not until the second year of war that the fragmented Free Syrian Army is definitely known to include radical extremists. The group Al-Nusra Front pledges allegiance to al Qaeda, further splintering the opposition.

In June 2013, the White House says it has evidence that Assad has been using sarin nerve gas on civilians - a report later backed by the UN. The discovery pushes US President Barack Obama and other Western leaders toward considering the use of military force. However, Russia's proposal to remove the chemical weapons ultimately wins out.

Reports of a new jihadist group calling itself the Islamic State of Iraq and the Levant (ISIL) emerge in the final weeks of 2013. Taking land in northern Syria and Iraq, the group sparks infighting among the opposition, with some 500 dead by early 2014. The unexpected emergence of IS ultimately draws the US, France, Saudi Arabia and other nations into the war.