In the period from 2010 to 2014, the number of casualties in the North Caucasus insurgency declined each year, with the overall death toll falling by more than half.[19] Reasons suggested for the decline include the deaths of high-ranking insurgency commanders, the increased targeting by security forces of the support infrastructure relied on by the insurgents, and an exodus of insurgents to other conflict zones.[19] A special investigation by Reuters claimed that in the lead-up to the 2014 Sochi Olympics, Russian security services had allowed and encouraged militants to leave Russia to fight in the Syrian Civil War, in order to reduce the risk of domestic attacks.[20]