Abdalrhman Ismail/Reuters
Children push containers in strollers as they flee deeper into the remaining rebel-held areas of Aleppo, Syria December 12, 2016
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.