Though a comprehensive understanding of ISIS' network of operatives remains elusive, some of the leadership and individuals who have carried out acts of terror around the world have been identified. At least 12 who served or continue to serve as the top leaders of ISIS spent time at Camp Bucca, known as the largest, and one of the toughest, American prisons in Iraq.
Ibrahim Awad Ibrahim Ali al-Badri al-Samarai
Abu Bakr al-Baghdadi
Al-Baghdadi is the caliph (leader) of ISIS. He was born in Samarra, and educated in Islamic history and, possibly, Sharia law at the University of Baghdad. He's now in his early 40s and married to possibly two wives, with at least a couple of kids.
U.S. forces detained him as a "civilian internee" in what the Department of Defense says was his hometown of Fallujah, and was imprisoned Feb. 4, 2004 at Camp Bucca, a U.S. prison camp, in Umm Qasr, Iraq. He was released from U.S. custody in early December. Soon after, he may have joined Abu Musab al-Zarqawi's Mujahideen Shura Council, an umbrella organization of Sunni insurgent groups that included al Qaeda in Iraq. He rose in power and was third in command when the top two leaders of ISIS in Iraq were killed in early 2010.
Abu Bakr al-Baghdadi - at large
A still photo from video posted on a militant website July 5, 2014, which has been authenticated based on its contents and other AP reporting, purports to show the leader of the Islamic State group, Abu Bakr al-Baghdadi, delivering a sermon at a mosque in Iraq during his first public appearance.
Salah Abdeslam- captured
A handout picture shows Belgian-born Salah Abdeslam, 26, seen on a call for witnesses notice released by the French Police Nationale information services on their Twitter account, Nov. 15, 2015.
There is a manhunt seeking Abdeslam, a brother of one of the known suicide bombers in the Paris attacks, who may be the only survivor among the perpetrators. On their Twitter feed the French National police described him as dangerous. He reportedly rented the black car used in the attack on the Bataclan concert hall and returned to Belgium the day after.
The fingerprints of Abdeslam were found in a Brussel's apartment raided by police in March 2016. Police came under fire during the raid leading to four officers being slightly injured and one suspect killed, according to Belgian authorities.
Foued Mohamed-Aggad - dead
A man identified by French media as the third ISIS attacker who stormed the Bataclan concert hall in Paris, Foued Mohamed-Aggad, on Nov. 13, 2015 is seen in a photo purportedly taken in Syria. Mohamed-Aggad was a French citizen.
Mohamed-Aggad left Strasbourg for Syria in late 2013, according to a French judicial official. France's BFM TV reported that police were tipped off to Mohamed-Aggad's role in the attacks by his mother, who received a text message on Dec. 7, apparently from the ISIS militant's widow in Syria, informing her that he had died in France on the day of the attacks.
Abdelhamid Abaaoud - dead
An undated photograph of a man identified as Abdelhamid Abaaoud published in the Islamic State's online magazine Dabiq and posted on a social media website.
Abaaoud was a 27-year-old from the Molenbeek suburb of Brussels, home to other members of the militant Islamist cell suspected of having carried out attacks.
The Belgian is believed to have been the ringleader of the Paris attacks, which left 130 people dead, Nov. 13, 2015. He was killed during a French police raid on an apartment in Saint-Denis, France on Nov. 18. His body was found riddled with bullets and shrapnel from a detonated grenade. Fingerprint analysis confirmed his identity, according to French authorities. Two others were killed in the raid.
Bilal Hadfi - dead
Bilal Hadfi, age 29 or 30, is believed to have been one of the perpetrators of the Paris attacks on Nov. 13, 2015, blowing himself up at the Stade de France. While a French citizen, Hadfi lived in Belgium.
According to Flemish newspaper Het Laatste Nieuws, he became radicalized very quickly in the spring of 2014. Belgian sources close to the investigation said Hadfi traveled to Syria where he joined the ranks of ISIS.
He was not known to French security services, but was on a Belgian watch list prior to the Paris attacks.
Suspect in Stade de France attack
French police tweeted this photo Nov. 22, 2015 of the third man suspected of blowing himself up in the Stade de France attack outside Paris, Nov. 13, asking for information about him.
Message reads: "This individual is the third dead perpetrator of one of the attacks carried out on 13 November at the Stade de France."
The BBC identified the suspect as someone traveling under the name of M al-Mahmod, after matching the photo to one found on arrival photos at Leros in Greece.
Jihadi John - dead
British militant colloquially dubbed "Jihadi John," identified as Mohamed Emwazi, 27, appeared in a number of ISIS execution and threat videos, as seen in one released Jan. 20, 2015.
A U.S. official told CBS News on Nov 13, 2015 that while they couldn't completely confirm the death of Mohamed Emwazi, they were "pretty goddamn certain" he was killed as he got into a vehicle in the Syrian city of Raqqa. A drone had been tracking Emwazi, waiting for a clear shot. A missile was fired late Nov. 12 at the target.
Jihadi John - dead
Emwazi had been described by a former hostage as a bloodthirsty psychopath who enjoyed threatening Western hostages. He is seen in the videos showing the killings of journalists Steven Sotloff and James Foley, U.S. aid worker Abdul-Rahman Peter Kassig, British aid workers David Haines and Alan Henning, Japanese journalist Kenji Goto and a number of other ISIS hostages.
Emwazi's identity was confirmed in February 2015 by U.S. intelligence officials. He grew up in West London and graduated in 2009 from the University of Westminster with a degree in computer science. Officials said Britain's intelligence community had Emwazi on its list of potential terror suspects for years but was unable to prevent him from traveling to Syria.
Fadel Ahmad Abdullah al-Hiyali - dead
Aka Abu Muataz aka Abu Muslim al-TurkmaniFadel Ahmad Abdullah al-Hiyali
aka Abu Muataz aka Abu Muslim al-Turkmani
Fadel Ahmad Abdullah al-Hiyali was in Senior Special Forces and military intelligence under former Iraqi leader Saddam Hussein. He may be the ISIS Governor of Deiz Azzour, Syria.
ISIS confirmed the death of the senior commander and top aide to Abu Bakr al-Baghdad Oct. 13, 2015. He was killed in an airstrike on Aug. 18 in Mosul, U.S. officials previously said.
Adnan Ismail Najem al-Bilawi - dead
Aka Abu Abed Abdul Rahman al-Bilawi
Adnan Ismail Najem al-Bilawi was a captain in Saddam Hussein's military and military chief of ISIS. He was killed in action in Mosul, Iraq on June 5, 2014. He was believed to have played a significant role in tactical strategy for the assault on Mosul, which has since been called "Bilawi's revenge" in his honor.
Samir Abd Muhammed al-Klifawi - dead
Aka Haji Bakr
Samir Abd Muhammed al-Klifawi was Al-Baghdadi's assistant and former army colonel under Saddam Hussein in Iraq and supervised ISIS in Syria. He was killed in action in Syria in 2014.
Abdullah Ahmed al-Meshdani aka Abu Qasim
Aka Abu Qasim
Abdullah Ahmed al-Meshdani is responsible for hosting foreign fighters.
Abdul Wahed Khutnayer Ahmed
Aka Abu Ali, Abu Lu'ay
Abdul Wahed Khutnayer Ahmed is responsible for general security.
Abdul Rahman al-Afari
Aka Abu Suja
Abdul Rahman al-Afair coordinates follow-ups on widows, martyrs and prisoners.
Adnan Latif Hamid al-Sweidawi
Aka Abu Abdul Salem aka Abu Muhanedal-Sweidawi
aka Abu Ayman al-Iraqi
Adnan Latif Hamid al-Sweidawi was a military officer under Saddam Hussein. Now he heads the ISIS military council and is Governor of Anbar Province in western Iraq.
He was detained in 2007 for three years at Camp Bucca. Following his release he moved to Syria.
Fares Raif al-Naima
Aka Abu Shema
Fares Raif al-Naima is the guardian of warehouses.
Abu Muhammad al Adnani al-Shami
Abu Muhammad al Adnani al-Shami is the ISIS spokesman in Syria.