The Islamic State's beheading of American journalist James Foley has caused outrage and disgust around the world, from Syria to the White House. And according to many experts, this was exactly the intended effect.
"It’s a gut-wrenching experience to watch a man die, and quite another to know that his killers are happily and publicly doing it just to score propaganda points," former CIA counterterrorism expert Aki Peretz wrote in The Washington Post this week. "But that is what the Islamic State of Iraq and Syria (ISIS) has been doing by releasing a video this week showing the murder of American journalist James Foley."
The Islamic State has also used beheadings to terrorize rival fighters, civilians and minorities in Iraq and Syria, and possibly also to win support from other jihadists.
"The idea is that in war you should strike fear in the heart of your enemies and show your commitment to fight to the death," Center for American Progress researcher Mokhtar Awad told ThinkProgress this week.
As the Islamic State continues to surge into new territory in Iraq and Syria, it has used this brutal tactic many times in recent months. Here's a look at some of the people who have become victims of the militant group.
Tribe members in Syria
During the first two weeks of August, Islamic State fighters killed 700 members of the al-Sheitaat tribe in Syria's Deir al-Zor province, according to the Syrian Observatory for Human Rights. Many of them were beheaded, the organization said. Islamic State militants had been battling the tribe since seizing two oil fields in Syria in July.
Yazidis in Iraq
Also in early August, as the group stormed through the homeland of Iraq's Yazidi minority group, reports emerged that Islamic State militants were beheading Yazidi villagers.
"One of the saddest stories was one of our relatives. They beheaded all his 15 family members in front of him and then took him with them," Abu Ali, one of tens of thousands of people who hid from militants on Iraq's Mount Sinjar, told Reuters.
In July, videos were circulated that showed militants mounting people's severed heads on a roundabout in Raqqa, a Syrian city under Islamic State control. One video said that the people killed were Syrian soldiers.
A few days before the videos emerged, the Syrian Observatory for Human Rights said that the Islamic State captured dozens of Syrian soldiers in Raqqa province.
"At least 50 soldiers were ambushed, some of them were killed in fighting but most of them were beheaded," Rami Abdel Rahman, director of the organization, told Agence France Presse.
Iraqis in Mosul
After Islamic State militants captured the major Iraqi city of Mosul in June, reports surfaced that people had seen mass beheadings. One BBC reporter said he spoke to a woman who said she saw "a row of decapitated bodies left in front of the main hospital in Mosul."
Residents of a Syrian border village
In just one instance of the Islamic State's brutal treatment of civilians in Syria, the group reportedly rounded up more than 100 men in a border village in Syria in January. It then beheaded at least 10 people, Al Jazeera reports.
"They lined us up against the wall and the emir told them not to waste bullets," village resident Muhammad Jader told the site. "Suddenly they grabbed one guy and pinned him down on his stomach. Then one man from ISIL put his knee on his back, shouted 'Allahu Akbar' and cut off his head with a knife."