In exclusive interviews, photos and research, The Associated Press has documented 72 of the mass graves that Islamic State extremists have left behind. It is the most comprehensive survey so far, but many more will likely be found as IS retreats.
In Syria, AP obtained 17 mass grave locations, including one with hundreds of bodies from a single tribe.
Total, the number of dead ranges from 5,200 to well over 15,000.
Scraped earth shows the likely site at Badoush Prison near Mosul, where more than 600 inmates died, according to exclusive satellite photos from the imagery intelligence firm AllSource Analysis.
Justice has been done at least once - in the deaths of about 1,700 Iraqi soldiers machine-gunned at Camp Speicher. On Aug. 21, 36 men were hanged for those killings.