Foreign fighters in the Syrian civil war have come to Syria and joined all four sides in the war. In addition to Sunni foreign fighters arriving to defend the Islamic State of Iraq and the Levant or join the Syrian rebels, Shia fighters from several countries have joined pro-government militias in Syria (assisted by private military contractors), and leftists have become . Estimates of the total number of foreign Sunnis who have fought for the Syrian rebels over the course of the conflict range from 5,000 to over 10,000, while foreign Shia fighters numbered around 10,000 or less in 2013 rising to between 15,000 and 25,000 in 2017. While more than 30,000 foreign fighters heeded the call to come to the Islamic State of Iraq and the Levant, not all of these were deployed in Syria, as the Islamic State also held a large part of Iraq for some years. (en)