Iraqi Shiite volunteers with the Labayk ya Hussein Brigade take part in a training session in the holy city of Najaf in late June. Clerics in the city called for Shiites to step forward and fight the Sunni group formerly known as the Islamic State of Iraq and Syria (which now calls itself simply the Islamic State).
Haidar Hamdan/AFP/Getty Images
Fighters of the Islamic State of Iraq and Syria parade in a commandeered Iraqi security forces armored vehicle in Mosul, Iraq, on June 23. Human Rights Watch says the group executed at least 160 unarmed Iraqis after it took control of the city of Tikrit.