When Americans leave for jihad

Peter Bergen and David Sterman
5 minute read
Updated 2:49 PM EDT, Fri August 29, 2014
Wounded passengers are treated following a suicide bombing at the Brussels Airport on March 22, 2016. <a href="http://www.cnn.com/2016/03/30/europe/brussels-investigation/index.html">The attacks on the airport and a subway </a>killed 32 people and wounded more than 300. ISIS claims its "fighters" launched the attacks in the Belgian capital.
Wounded passengers are treated following a suicide bombing at the Brussels Airport on March 22, 2016. The attacks on the airport and a subway killed 32 people and wounded more than 300. ISIS claims its "fighters" launched the attacks in the Belgian capital.
Ketevan Kardava/Getty Images
Syrians gather at the site of a double car bomb attack in the Al-Zahraa neighborhood of the Homs, Syria, on February 21, 2016. <a href="http://www.cnn.com/2016/02/21/middleeast/syria-civil-war/index.html" target="_blank">Multiple attacks in Homs and southern Damascus</a> kill at least 122 and injure scores, according to the state-run SANA news agency. ISIS claimed responsibility.
Syrians gather at the site of a double car bomb attack in the Al-Zahraa neighborhood of the Homs, Syria, on February 21, 2016. Multiple attacks in Homs and southern Damascus kill at least 122 and injure scores, according to the state-run SANA news agency. ISIS claimed responsibility.
STRINGER/AFP/Getty Images
Syrian pro-government forces gather at the site of a deadly triple bombing Sunday, January 31, in the <a href="http://www.cnn.com/2016/01/31/middleeast/syria-damascus-explosions/index.html" target="_blank">Damascus suburb of Sayeda Zeynab</a>. ISIS claimed responsibility for the attack, according to a statement circulating online from supporters of the terrorist group.
Syrian pro-government forces gather at the site of a deadly triple bombing Sunday, January 31, in the Damascus suburb of Sayeda Zeynab. ISIS claimed responsibility for the attack, according to a statement circulating online from supporters of the terrorist group.
LOUAI BESHARA/AFP/Getty Images
Yemenis check the scene of a car bomb attack Sunday, December 6, in Aden, Yemen. <a href="http://www.cnn.com/2015/12/06/middleeast/yemen-aden-governor-killed/index.html">Aden Gov. Jaafar Saad and six bodyguards died in the attack</a>, for which the terror group ISIS claimed responsibility.
Yemenis check the scene of a car bomb attack Sunday, December 6, in Aden, Yemen. Aden Gov. Jaafar Saad and six bodyguards died in the attack, for which the terror group ISIS claimed responsibility.
Wael Qubady/AP
Investigators check the scene of a mosque attack Friday, November 27, in northern Bangladesh's Bogra district. <a href="http://www.cnn.com/2015/11/27/asia/bangladesh-isis-attack-claim/index.html" target="_blank">ISIS has claimed responsibility for the attack</a> that left at least one person dead and three more wounded.
Investigators check the scene of a mosque attack Friday, November 27, in northern Bangladesh's Bogra district. ISIS has claimed responsibility for the attack that left at least one person dead and three more wounded.
AP
Wounded people are helped outside the Bataclan concert hall in Paris following a series of coordinated attacks in the city on Friday, November 13. The militant group ISIS claimed responsibility <a href="http://www.cnn.com/2015/11/13/world/gallery/paris-attacks/index.html" target="_blank">for the attacks,</a> which killed at least 130 people and wounded hundreds more.
Wounded people are helped outside the Bataclan concert hall in Paris following a series of coordinated attacks in the city on Friday, November 13. The militant group ISIS claimed responsibility for the attacks, which killed at least 130 people and wounded hundreds more.
YOAN VALAT/EPA/LANDOV
Emergency personnel and civilians gather at the site of a <a href="http://www.cnn.com/2015/11/16/middleeast/beirut-explosions/" target="_blank">twin suicide bombing</a> in Beirut, Lebanon, on Thursday, November 12. The bombings killed at least 43 people and wounded more than 200 more. ISIS appeared to claim responsibility in a statement posted on social media.
Emergency personnel and civilians gather at the site of a twin suicide bombing in Beirut, Lebanon, on Thursday, November 12. The bombings killed at least 43 people and wounded more than 200 more. ISIS appeared to claim responsibility in a statement posted on social media.
Bilal Hussein/AP
Smoke rises over the northern Iraqi town of Sinjar on November 12. Kurdish Iraqi fighters, backed by a U.S.-led air campaign, <a href="http://www.cnn.com/2015/11/13/middleeast/iraq-free-sinjar-isis/" target="_blank">retook the strategic town, </a>which ISIS militants overran last year. ISIS wants to create an Islamic state across Sunni areas of Iraq and Syria.
Smoke rises over the northern Iraqi town of Sinjar on November 12. Kurdish Iraqi fighters, backed by a U.S.-led air campaign, retook the strategic town, which ISIS militants overran last year. ISIS wants to create an Islamic state across Sunni areas of Iraq and Syria.
Bram Janssen/AP
Syrian government troops walk inside the Kweiras air base on Wednesday, November 11, after they broke a siege imposed by ISIS militants.
Syrian government troops walk inside the Kweiras air base on Wednesday, November 11, after they broke a siege imposed by ISIS militants.
SANA/AP
Members of the Egyptian military approach the wreckage of a Russian passenger plane Sunday, November 1, in Hassana, Egypt. <a href="http://www.cnn.com/2015/10/31/world/gallery/russian-plane-crash/index.html" target="_blank">The plane crashed</a> the day before, killing all 224 people on board. ISIS claimed responsibility for downing the plane, but the group's claim wasn't immediately verified.
Members of the Egyptian military approach the wreckage of a Russian passenger plane Sunday, November 1, in Hassana, Egypt. The plane crashed the day before, killing all 224 people on board. ISIS claimed responsibility for downing the plane, but the group's claim wasn't immediately verified.
Maxim Grigoriev/Russian Ministry for Emergency Situations/AP
An explosion rocks Kobani, Syria, during a reported car bomb attack by ISIS militants on Tuesday, October 20.
An explosion rocks Kobani, Syria, during a reported car bomb attack by ISIS militants on Tuesday, October 20.
Gokhan Sahin/Getty Images
Shiite fighters, fighting alongside Iraqi government forces, fire a rocket at ISIS militants as they advance toward the center of Baiji, Iraq, on Monday, October 19.
Shiite fighters, fighting alongside Iraqi government forces, fire a rocket at ISIS militants as they advance toward the center of Baiji, Iraq, on Monday, October 19.
AHMAD AL-RUBAYE/AFP/Getty Images
Smoke rises above a damaged building in Ramadi, Iraq, following a coalition airstrike against ISIS positions on Saturday, August 15.
Smoke rises above a damaged building in Ramadi, Iraq, following a coalition airstrike against ISIS positions on Saturday, August 15.
AP
Iraqi men look at damage following a bomb explosion that targeted a vegetable market in Baghdad on Thursday, August 13. ISIS claimed responsibility for the attack.
Iraqi men look at damage following a bomb explosion that targeted a vegetable market in Baghdad on Thursday, August 13. ISIS claimed responsibility for the attack.
AHMAD AL-RUBAYE/AFP/AFP/Getty Images
In this image taken from social media, an ISIS fighter holds the group's flag after the militant group <a href="http://www.cnn.com/2015/08/07/world/syria-isis-al-qaryatayn-christians/index.html" target="_blank">overran the Syrian town of al-Qaryatayn</a> on Thursday, August 6, the London-based Syrian Observatory for Human Rights reported. ISIS uses modern tools such as social media to promote reactionary politics and religious fundamentalism. Fighters are destroying holy sites and valuable antiquities even as their leaders propagate a return to the early days of Islam.
In this image taken from social media, an ISIS fighter holds the group's flag after the militant group overran the Syrian town of al-Qaryatayn on Thursday, August 6, the London-based Syrian Observatory for Human Rights reported. ISIS uses modern tools such as social media to promote reactionary politics and religious fundamentalism. Fighters are destroying holy sites and valuable antiquities even as their leaders propagate a return to the early days of Islam.
From ISIS
An ISIS fighter poses with spoils purportedly taken after capturing the Syrian town of al-Qaryatayn.
An ISIS fighter poses with spoils purportedly taken after capturing the Syrian town of al-Qaryatayn.
From ISIS
Smoke rises as Iraqi security forces bomb ISIS positions in the eastern suburbs of Ramadi, Iraq, on August 6.
Smoke rises as Iraqi security forces bomb ISIS positions in the eastern suburbs of Ramadi, Iraq, on August 6.
AP
Buildings reduced to piles of debris can be seen in the eastern suburbs of Ramadi on August 6.
Buildings reduced to piles of debris can be seen in the eastern suburbs of Ramadi on August 6.
AP
The governor of the Asir region in Saudi Arabia, Prince Faisal bin Khaled bin Abdulaziz, left, visits a man who was wounded in <a href="http://www.cnn.com/2015/08/06/middleeast/saudi-arabia-mosque-attack/" target="_blank">a suicide bombing attack on a mosque</a> in Abha, Saudi Arabia, on August 6. ISIS claimed responsibility for the explosion, which killed at least 13 people and injured nine others.
The governor of the Asir region in Saudi Arabia, Prince Faisal bin Khaled bin Abdulaziz, left, visits a man who was wounded in a suicide bombing attack on a mosque in Abha, Saudi Arabia, on August 6. ISIS claimed responsibility for the explosion, which killed at least 13 people and injured nine others.
Saudi Press Agency/AP
Saudi officials and investigators check the inside of the mosque on August 6.
Saudi officials and investigators check the inside of the mosque on August 6.
Saudi Press Agency/AP
Mourners in Gaziantep, Turkey, grieve over a coffin Tuesday, July 21, during a funeral ceremony for the victims of a suspected ISIS suicide bomb attack. <a href="http://www.cnn.com/2015/07/20/world/turkey-suruc-explosion/">That bombing killed at least 31 people</a> in Suruc, a Turkish town that borders Syria. Turkish authorities blamed ISIS for the attack.
Mourners in Gaziantep, Turkey, grieve over a coffin Tuesday, July 21, during a funeral ceremony for the victims of a suspected ISIS suicide bomb attack. That bombing killed at least 31 people in Suruc, a Turkish town that borders Syria. Turkish authorities blamed ISIS for the attack.
Gokhan Sahin/Getty Images
Protesters in Istanbul carry anti-ISIS banners and flags to show support for victims of the Suruc suicide blast during a demonstration on Monday, July 20.
Protesters in Istanbul carry anti-ISIS banners and flags to show support for victims of the Suruc suicide blast during a demonstration on Monday, July 20.
YASIN AKGUL/AFP/Getty Images
People in Ashmoun, Egypt, carry the coffin for 1st Lt. Mohammed Ashraf, who was killed when the ISIS militant group <a href="http://www.cnn.com/2015/07/02/world/isis-egypt-expanding-reach/index.html" target="_blank">attacked Egyptian military checkpoints</a> on Wednesday, July 1. At least 17 soldiers were reportedly killed, and 30 were injured.
People in Ashmoun, Egypt, carry the coffin for 1st Lt. Mohammed Ashraf, who was killed when the ISIS militant group attacked Egyptian military checkpoints on Wednesday, July 1. At least 17 soldiers were reportedly killed, and 30 were injured.
Ashour Abosalm/AP
Syrians wait near the Turkish border during clashes between ISIS and Kurdish armed groups in Kobani, Syria, on Thursday, June 25. The photo was taken in Sanliurfa, Turkey. ISIS militants disguised as Kurdish security forces infiltrated Kobani on Thursday and killed "many civilians," said a spokesman for the Kurds in Kobani.
Syrians wait near the Turkish border during clashes between ISIS and Kurdish armed groups in Kobani, Syria, on Thursday, June 25. The photo was taken in Sanliurfa, Turkey. ISIS militants disguised as Kurdish security forces infiltrated Kobani on Thursday and killed "many civilians," said a spokesman for the Kurds in Kobani.
Halil Fidan/Anadolu Agency/Getty Images
Residents examine a damaged mosque after an Iraqi Air Force bombing in the ISIS-seized city of Falluja, Iraq, on Sunday, May 31. At least six were killed and nine others wounded during the bombing.
Residents examine a damaged mosque after an Iraqi Air Force bombing in the ISIS-seized city of Falluja, Iraq, on Sunday, May 31. At least six were killed and nine others wounded during the bombing.
Sami Jawad/Xinhua/SIPA
People search through debris after an explosion at a Shiite mosque in Qatif, Saudi Arabia, on Friday, May 22. ISIS <a href="http://edition.cnn.com/2015/05/22/middleeast/saudi-arabia-mosque-blast/index.html" target="_blank">claimed responsibility for the attack,</a> according to tweets from ISIS supporters, which included a formal statement from ISIS detailing the operation.
People search through debris after an explosion at a Shiite mosque in Qatif, Saudi Arabia, on Friday, May 22. ISIS claimed responsibility for the attack, according to tweets from ISIS supporters, which included a formal statement from ISIS detailing the operation.
EPA/STR/LANDOV
Iraqi soldiers fire their weapons toward ISIS group positions in the Garma district, west of the Iraqi capital of Baghdad, on Sunday, April 26. Pro-government forces said they had recently made advances on areas held by Islamist jihadists.
Iraqi soldiers fire their weapons toward ISIS group positions in the Garma district, west of the Iraqi capital of Baghdad, on Sunday, April 26. Pro-government forces said they had recently made advances on areas held by Islamist jihadists.
AHMAD AL-RUBAYE/AFP/Getty Images
A member of Afghanistan's security forces stands at the site where a suicide bomber on a motorbike blew himself up in front of the Kabul Bank in Jalalabad, Afghanistan, on Saturday, April 18. ISIS claimed responsibility for the attack. The explosion killed at least 33 people and injured more than 100 others, a public health spokesman said.
A member of Afghanistan's security forces stands at the site where a suicide bomber on a motorbike blew himself up in front of the Kabul Bank in Jalalabad, Afghanistan, on Saturday, April 18. ISIS claimed responsibility for the attack. The explosion killed at least 33 people and injured more than 100 others, a public health spokesman said.
Stringer/AP
Iraqi counterterrorism forces patrol in Ramadi on April 18.
Iraqi counterterrorism forces patrol in Ramadi on April 18.
Stringer/AP
Thousands of Iraqis cross a bridge over the Euphrates River to Baghdad as they flee Ramadi on Friday, April 17.
Thousands of Iraqis cross a bridge over the Euphrates River to Baghdad as they flee Ramadi on Friday, April 17.
Ali Mohammed/Anadolu Agency/Getty Images
Yazidis embrace after being released by ISIS south of Kirkuk, Iraq, on Wednesday, April 8.<a href="http://www.cnn.com/2015/04/08/world/isis-yazidis-released/"> ISIS released more than 200 Yazidis</a>, a minority group whose members were killed, captured and displaced when the Islamist terror organization overtook their towns in northern Iraq last summer, officials said.
Yazidis embrace after being released by ISIS south of Kirkuk, Iraq, on Wednesday, April 8. ISIS released more than 200 Yazidis, a minority group whose members were killed, captured and displaced when the Islamist terror organization overtook their towns in northern Iraq last summer, officials said.
Ali Mukarrem Garip/Anadolu Agency/Getty Images
Kurdish Peshmerga forces help Yazidis as they arrive at a medical center in Altun Kupri, Iraq, on April 8.
Kurdish Peshmerga forces help Yazidis as they arrive at a medical center in Altun Kupri, Iraq, on April 8.
SAFIN HAMED/AFP/Getty Images
A Yazidi woman mourns for the death of her husband and children by ISIS after being released south of Kirkuk on April 8. ISIS is known for killing dozens of people at a time and carrying out public executions, crucifixions and other acts.
A Yazidi woman mourns for the death of her husband and children by ISIS after being released south of Kirkuk on April 8. ISIS is known for killing dozens of people at a time and carrying out public executions, crucifixions and other acts.
Feriq Ferec/Anadolu Agency/Getty Images
People in Tikrit inspect what used to be a palace of former President Saddam Hussein on April 3.
People in Tikrit inspect what used to be a palace of former President Saddam Hussein on April 3.
Khalid Mohammed/AP