Four years ago today, Syria's conflict — then a revolution — first turned bloody. Popular protests were springing up across the Arab world, and Syria was no exception.

On March 18, 2011, in the southern city of Dara'a, demonstrators were calling the resignation of the mayor and the head of local security forces when police fired onto the crowd, killing six according to The New York Times.

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The demands of the Syrians who protested back then, and those who are still standing against Bashar al-Assad's regime, were similar to those echoed throughout the region. But security forces' violent response to those initial protests unleashed a nightmare on the country that only continues as the conflict now enters its fifth year.

No Syrian, no matter what side or faction, has been left untouched by the violence. With at least 210,000 dead and 840,000 injured, approximately 6 percent of the country's population has been killed or injured during the past four years.

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The conflict has also led to a refugee crisis of historic proportions — with almost 4 million registered refugees, and over 6 million people displaced internally.

Here are just a few facts to help you understand the horrible scale of Syria's conflict.