Last week, the US responded to a deadly chemical weapons attack believed to have been carried out by the Syrian government six years into the country's devastating civil war.
The war, which erupted in 2011 following a popular uprising against the authoritarian regime of Bashar al-Assad, has left nearly half a million people dead and sparked the largest refugee crisis since World War II.
These are the complicated and horrifying events that sparked the war, and, ultimately, the US response.
In the spring of 2011, a series of pro-democracy protests known as the Arab Spring were rocking countries across the Middle East. In Syria, people peacefully protested in the streets after President Bashar Assad's government arrested and tortured teenagers for writing some pro-revolution graffiti on their school wall.
Source: BBC
To quell the protests, government forces started opening fire during marches and sit-ins. With hundreds of people now killed by Assad's government, the protesters who initially called for more civil liberties started demanding a total overthrow of Assad's regime.
Source: The Guardian
With no end to the violence, some former government officers formed the Free Syrian Army to support the opposition. As sides battled for control over major cities such as Homs and Aleppo, the fighting escalated into a full-blown civil war by the end of 2011.
Source: BBC
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