In this April 3, 2015 photo, an Iraqi man prays for his slain relative at the site of a mass grave believed to contain the bodies of Iraqi soldiers killed by Islamic State group militants when they overran Camp Speicher military base in Tikrit, Iraq, in June 2014. An analysis by The Associated Press has found 72 mass graves left behind by Islamic State extremists in Iraq and Syria, and many more are expected to be discovered as the group loses territory. (AP Photo/Khalid Mohammed)