The announcement laid out a choice for jihadist groups -- pledge loyalty to ISIS or fight against it. Within months, groups from the Middle East, North Africa and Southeast Asia would pledge "bay'a," or religiously binding allegiance to Baghdadi.
But some of these pledges were more important to ISIS than others. When its black flag has appeared in new countries, it has mainly risen in stretches of ungoverned land that ISIS formally recognizes as "wilayats" -- or provinces. These wilayats have helped the terror group boast of expansion, even as it has lost territory in Iraq and Syria under the strain of international airstrikes and fighting against Arab and Kurdish forces in the region.
"The actual creation of ISIS's wilayats or governorates was a much more intentional and phased campaign," said Harleen Gambhir, a counterterrorism analyst at the Institute for the Study of War. "ISIS leadership is actually quite selective about which groups it chooses to affiliate with, and from there, about what types of assistance it provides to those groups."
Assistance can include anything from trained fighters and funds to military expertise or lessons in governance. But before senior leadership will consider a new franchise, the group must first publicly pledge allegiance, select a leader and present a strategy for the region where it operates, a process ISIS laid out in its English language magazine Dabiq in early 2015.
“ISIS has shown itself to be an actor that is keenly and acutely aware of international tensions and fault lines.”
This selectiveness, experts say, allows ISIS to project an aura of strength. Of roughly 40 groups in 16 countries that have pledged support or allegiance, ISIS has formally recognized nearly 20 wilayats in nine countries.
"They don't want to pick a real amateurish outfit that will get crushed, because they don't consider them affiliates. They consider them states, and they don't want to lose a state," said Patrick Skinner, a former CIA case officer who now serves as director of special projects at the Soufan Group, a security intelligence firm.
With recent losses in Iraq and Syria, the affiliate strategy has only grown more important, said Lina Khatib, the head of the Middle East and North Africa Program at Chatham House, an independent policy institute in London. Noting that the group's motto is "remaining and expanding," Khatib said that ISIS uses its affiliates as outposts, to propagate a notion of its global reach.
The more territory ISIS holds, the more it can also seek to legitimize its claims of being an Islamic caliphate. In some places, like Libya or Egypt's Sinai Peninsula, the wilayats have emerged as strongholds beyond Iraq and Syria. In others, the wilayats are relatively weak or have been contained by security forces. In still others, they've emerged as destabilizing threats to already vulnerable governments. But weak or strong, the wilayats cement ISIS's stature in the eyes of other extremist groups and allow it to create a propagandist narrative of constant expansion.
The Growing Danger
Groups in Libya and Egypt's Sinai Peninsula were among the earliest wilayats to be recognized. Today, both branches are seen as the most dangerous affiliates outside of Iraq and Syria, providing ISIS central with "strategic resiliency," according to Gambhir.
"The idea is that if ISIS actually loses all of its terrain within Iraq and Syria … then it can still claim the caliphate exists because of the terrain it holds in Libya, and possibly also the Sinai Peninsula."
Wilayat Barqa, Wilayat Fezzan, Wilayat Tarablus
The ISIS affiliate in Libya is the largest and arguably most potent branch to arise from the chaos in the region. The NATO-led intervention and armed uprising that brought down Muammar Qaddafi in 2011 left a power vacuum that rival governments and hundreds of armed militias with conflicting agendas have not been able to fill.
Within that void, ISIS has moved in, unleashing a familiar and grisly campaign of bombings, beheadings, kidnappings, shootings and other attacks. Today, the group is thought to have somewhere between 5,000 and 6,500 fighters in Libya, according to Pentagon estimates.
The first reports of an ISIS presence in Libya placed it in the eastern port city of Derna in October 2014. Two months later, the group was claiming responsibility for attacks on embassies and security buildings in the nation's capital, Tripoli.
ISIS has since been kicked out of Derna by Islamist militias, but now controls the city of Sirte, parts of Benghazi and roughly 100 miles of coastline. Its growing presence has spurred Western powers to action. Last November, and again in February, U.S. airstrikes hit ISIS targets in Libya.
The wilayats in Libya "raise the bar for what is required to destroy ISIS," said Gambhir. "Now it's not only that ISIS has to be defeated within Iraq and Syria, it has to be defeated in Libya as well."
Major attacks in libya
Jan. 27, 2015 Gunmen storm a luxury hotel in Tripoli, killing five tourists and five guards.
Feb. 15, 2015 21 Egyptian Christians dressed in orange jump suits are beheaded in Libya. ISIS shows the execution in a video called "a message signed with blood to the nation of the cross."
Feb. 20, 2015 At least 40 are killed in a triple-bombing in the Libyan town of Qubbah. ISIS fighters say they struck in retaliation for Egyptian air strikes.
May 31, 2015 A suicide bomber kills at least four fighters at a checkpoint west of the city of Misurata.
Jan. 8, 2016 A suicide bomber hits a training camp for coast guard cadets, killing at least 65, injuring more than 150.
May 6, 2016 ISIS fighters launch a coordinated attack on the Abugrein checkpoint, with a suicide bombing and gunfire that kills eight security forces. The attack was launched from its stronghold in Sirte, and ISIS claims it seized six towns near the checkpoint.
Feb. 24, 2016 ISIS fighters briefly take over a security headquarters in Sabratha, killing and beheading 12 security officers.
A similar scenario has unfolded in Egypt's Sinai Peninsula, where in November 2014, the terror group Ansar Beit al-Maqdis -- responsible for the deaths of hundreds of Egyptian security forces -- pledged allegiance to ISIS.
"Sinai was kind of an obvious choice," said Skinner. "They want to be seen fighting Egypt. And there was a long-simmering insurgency there that had proven almost impossible to stamp out."
Analysts say that after the pledge, a new level of sophistication could be seen in attacks in Sinai, suggesting ISIS provided militants there with training in bomb-making, and the basics of how to pull off large-scale, coordinated attacks. That sophistication was on display in a wave of assaults against Egyptian army and police positions on July 1, 2015 that killed at least 50.
"One really good, skilled bomb maker can do a lot of damage," according to Skinner, who noted that the affiliates in Sinai and Libya have "actual fighters" -- not just members, but militants who've fought in Iraq and Syria for years.
"It's really hard to overstate the impact of 50 trained people that know what they're doing," he said. "Training matters, and ISIS has had four years plus of actual, live-fire combat training and a lot of innovation."
In October 2015, ISIS claimed responsibility for the bombing of a Russian airliner in Sinai. All 224 on board were killed.
Major attacks in egypt
Jan. 29, 2015 At least 26 Egyptian security officers are killed on attacks on more than 12 army and police targets.
April 2, 2015 Attacks on two army checkpoints leave 13 soldiers and two civilians dead. At least 15 attackers also die.
April 12, 2015 Twin bombings kill at least 14 in the Sinai peninsula -- 11 of the dead are security forces.
July 1, 2015 At least 50 Egyptian soldiers die in a wave of simultaneous attacks on 15 army and police positions.
Oct. 31, 2015 ISIS claims responsibility for downing a Russian passenger jet, killing all 224 people on board.
Nov. 24, 2015 An attack on the Swiss Inn hotel in el-Arish kills seven, including two judges.
The Destabilizing Threats
Wilayat Aden-Abyan, Wilayat Ataq, Wilayat Bayda, Wilayat Hadramawt, Wilayat Lahij, Wilayat Luaa al-Akhdar, Wilayat Sanaa, Wilayat Shabwa
Even in countries where ISIS doesn't have an established hold, it can play an outsized role, destabilizing existing conflicts and amplifying sectarian divides.
Yemen's government and allied militias were already fighting Houthi rebels from the country's Zaydi Shiite minority when ISIS announced its entrance into the conflict with devastating suicide bombings targeting Zaydi worshippers on March 20, 2015. At least 130 people were killed in attacks on two mosques.
The attacks heralded a new, more deadly phase of the conflict, with the United States pulling its military personnel from the country and Saudi Arabia -- an ally of Yemen's President Abdu Rabbu Mansour Hadi -- launching a military intervention days later.
"We can't discount the potential of the asymmetric affiliates -- the ones that aren't necessarily the largest or most powerful fighting groups in the area they're operating in, but have the potential to change conditions in a way that triggers broader instability and insecurity," Gambhir said. "ISIS has shown itself to be an actor that is keenly and acutely aware of international tensions and fault lines."
ISIS has recognized at least eight wilayats in Yemen, though it's believed to only have several hundred fighters in the country. By comparison, the dominant terrorist group in Yemen, the Al Qaeda affiliate known as Al Qaeda in the Arabian Peninsula, has gone further to forge alliances with local jihadists, strengthening its foothold in Yemen and bringing its ranks into the thousands.
Skinner pointed out that in areas where ISIS is more powerful, it's "ISIS versus everybody else. Al Qaeda is the exact opposite. Al Qaeda embraces local tribes." That kind of strategy, he argued, leaves ISIS surrounded by enemies, whereas Al Qaeda's approach of building local alliances has allowed its affiliates to survive, and even thrive, despite "unbelievable pressure" on the parent organization.
Major attacks in yemen
March 20, 2015 Coordinated suicide bombings kill 130 in Zaydi Shia mosques.
June 17, 2015 A series of car bombings in Sanaa kill at least 30 people.
Sept. 2, 2015 Twin bombings at a mosque kill at least 20 in Sanaa.
Sept. 24, 2015 At least 25 are killed and 36 wounded in an attack outside a mosque during the Eid holiday.
Dec. 6, 2015 The governor of Aden and eight bodyguards are killed in car bombing.
Jan. 29, 2016 A car bombing outside the presidential palace in Aden kills 11. The president is unharmed.
March 4, 2016 ISIS kills 16, including six nuns, at a nursing home founded by Mother Teresa.
May 12, 2016 ISIS claims an attack on a naval base in the city of Mukalla, which was previously occupied by Al Qaeda's Yemen affiliate. Between 10 to 15 Yemeni troops are killed in the suicide bombing, and other attacks.
May 15, 2016 ISIS claims responsibility for the second suicide bombing in Mukalla in four days, which killed 25 policemen and potential recruits at a security compound.
Afghanistan is another country where ISIS has had a destabilizing influence despite stiff competition from an existing and successful militant group -- this time the nationalist, ethnically Pashtun Taliban.
The earliest fighters to join ISIS in Afghanistan were primarily defectors from the Pakistani and Afghan Taliban. As one defector told FRONTLINE in 2015, "God says when there is a caliphate, you must join the caliphate. There is a caliphate now, so we've left the Taliban. We're fighting holy war under caliph's leadership."
In January 2015, ISIS central established Wilayat Khorasan to encompass areas in Afghanistan and Pakistan. Today, the group is thought to have anywhere from 1,000 to 3,000 fighters.
ISIS has assassinated rival Taliban leaders, beheaded civilians from the minority Hazara community, and in January it claimed responsibility for an attack outside the Pakistani consulate in Jalalabad.
The emergence of ISIS in Afghanistan has complicated President Barack Obama's efforts to end U.S. involvement in the war there. Last October, Obama delayed a drawdown of 9,800 troops until 2016, saying, "The bottom line is, in key areas of the country, the security situation is still very fragile, and in some places there is risk of deterioration." Three months later, the White House granted the Pentagon new authority to target ISIS in Afghanistan, expanding the military's ability to strike the group outside Iraq and Syria.
Major attacks in afghanistan
April 19, 2015 A suicide bombing in Jalalabad kills at least 33 people and injures more than 100 in front of the New Kabul Bank.
Aug. 11, 2015 An ISIS video shows 10 village elders, some with ties to the Taliban, being blown up in Nangarhar province.
Nov. 9, 2015 Three women and a child are among seven ethnic Hazaras beheaded by ISIS-linked militants in Zabul province.
Jan. 13, 2016 An attack on the Pakistani consulate in Jalalabad kills at least seven security forces. Three attackers also die.
Wilayat Bahrain, Wilayat Hijaz, Wilayat Najd
In Saudi Arabia, ISIS's three declared wilayats don't hold territory, but they have carried out roughly 20 targeted killings or attacks, including one in neighboring Kuwait. The attacks they've claimed bear ISIS hallmarks -- suicide bombings, the targeting of religious minorities to inflame sectarian tensions, and attacking security forces.
Saudi Arabia holds special significance for ISIS, according to Cole Bunzel, a scholar of Near Eastern studies at Princeton University, who notes that for its senior leaders, the kingdom is "a failed version of the Islamic State." Its message in Saudi Arabia, where Sunni Muslims outnumber Shiites, is that ISIS is "the champion of Sunni Islam at a time when the Shiite are seen to be taking over the Middle East," said Bunzel.
Major attacks in saudi arabia
May 22, 2015 A suicide bomber kills at least 21 and injures 120 during Friday prayers at a Shiite mosque in Qatif province.
Aug. 7, 2015 A suicide bombing at a mosque kills 15 people, many of them security forces.
May 29, 2015 A suicide bomber again targets a Shiite mosque, killing at least four people.
Affiliates Under Pressure
Despite the effort to ensure affiliates help maintain a narrative of victory, some offshoots have proven less valuable than others. That's been the case in Algeria and Russia's North Caucasus region, where security forces in both countries have been more successful in containing the threat. In Nigeria, a potent homegrown terrorist threat that was eager to pledge allegiance to ISIS has found itself the target of joint military operations, putting it on the defensive.
Wilayat Gharb Ifriqiyyah
The ISIS affiliate in Nigeria is better known by its other name -- Boko Haram. The extremist group has been waging a brutal and deadly insurgency against the Nigerian government, attacking, kidnapping, raping and killing civilians since 2009. According to the Global Terrorism Index, Boko Haram killed more people (6,644) than ISIS (6,073) in 2014.
That same year, Boko Haram declared its own caliphate in territory it had seized in northeastern Nigeria. Six months later, in March 2015, it pledged allegiance to Baghdadi, giving ISIS access to new recruits and weapons in Africa.
While experts say it's difficult to determine the exact nature of the relationship between the groups, in October 2015, the head of U.S. Africa Command, Gen. David Rodriguez, said Boko Haram's use of roadside bombs and suicide bombings evolved after its pledge to ISIS.
Experts have also noticed more polish in Boko Haram's propaganda offerings, and just last month, U.S. military officials said the two groups have begun to collaborate more closely.
Nigeria, Chad, Cameroon and Niger's military forces began working together against Boko Haram last year, wresting at least some territory back from under its control. But as Crisis Group noted in a recent report, given Boko Haram's vast reach across Nigeria, it remains "unlikely to be eliminated in a decisive battle."
Major attacks in nigeria
Jan. 7, 2015 Boko Haram carries out its largest attack to date, killing an estimated 2,000 people in the towns of Baga and Doro Baga.
March 3, 2015 An attack in Borno state leaves 68 people dead -- including children as young as 13.
June 11, 2015 Militants storm three villages in Borno state, shooting locals and burning homes. They kill 43.
June 12, 2015 Boko Haram burns down six villages near Sambisa Forest in the northeast, killing 37.
Aug. 18, 2015 As many as 160 die, locals said, when Boko Haram storms a village in the northeast. Many are shot. Others drown in a nearby river trying to escape.
Sept. 20, 2015 A series of coordinated bombings in the capital of Borno State leave more than 100 civilians dead.
Jan. 31, 2016 At least 65 are killed in an attack that combined suicide bombing, shooting and arson. It's the third Boko Haram attack in a week.
Feb. 10, 2016 Two female suicide bombers kill 58 at a camp for displaced people. A third bomber surrenders.
An ISIS branch took shape in Russia's Caucasus region in January 2015 when a splinter from the Caucasus Emirate -- a militant group that claimed high-profile attacks on the Moscow metro and the Domodedovo airport in 2010 and '11, and a series of attacks ahead of the Sochi Olympics in 2013 -- pledged allegiance to Baghdadi. The new affiliate, Wilayat Qawqaz, has staged a handful of bombings against police checkpoints since becoming an official wilayat last June, but it has yet to execute a more large-scale attack.
"The Caucasus group has shown itself to be relatively unskilled," Gambhir said. "The trend that we've seen is that because Russian state security and internal security in the Caucasus is so strong, the fighters who felt like they actually wanted to make a difference were the first ones to leave and to head to the Syrian front to get training."
Some experts have warned that harsh counterterrorism methods may backfire, leading to the risk of a future rise in violence.
In the meantime, an estimated 2,400 Russians have traveled to Syria to join ISIS, according to the Soufan Group, many of them from the turbulent North Caucasus regions of Chechnya and Dagestan.
Another ISIS affiliate that has been all but suppressed is in Algeria. It formed when a faction of Al Qaeda in the Islamic Maghreb, Al Qaeda's North African affiliate, broke away, pledged allegiance and was recognized by Baghdadi in November 2014.
Even though the Algerian branch -- known as Wilayat al-Jaza'ir -- was among the first affiliates to be recognized, it hasn't carried out the kind of spectacular attacks that ISIS fighters have staged in other countries with more frequency. To date, its most high-profile action was the kidnapping and subsequent beheading of a French citizen, Herve Gourdel, in September 2014.
Algerian security forces cracked down on the group in the months following Gourdel's death. Its leader, Abdelmalek Gouri, was killed in December 2014, and the defense ministry said at least 22 militants linked to the affiliate were killed in an ambush in May 2015.
"It's actually the example I point to for the benefits of early action against these budding affiliates," Gambhir said.
Experts are keeping an eye on several locations where ISIS may recognize formal affiliates in the future. Abu Sayyaf, a militant group in the Philippines that has already vowed allegiance to ISIS and carried out multiple abductions of foreign nationals, is seen as a likely candidate, as is an affiliate in Bangladesh, where ISIS-linked terrorists claimed credit for bombings of Shiite mosques last fall and a string of recent hacking deaths, including an academic and a Hindu tailor.
Other possibilities include Tunisia, which has exported the highest number of foreign fighters to ISIS of any country, and Somalia. ISIS claimed responsibility for two high-profile mass killings in Tunisia last year, both of which targeted tourist spots. In Somalia, ISIS has also been trying to attract enough defectors from the Al Qaeda-linked group Al Shabaab to declare an affiliate.
Beyond its affiliates, ISIS has absorbed an unprecedented number of foreign fighters from dozens of countries in the Middle East, Asia, Africa and Europe. In its propaganda, ISIS advertises its ability to attract foreign recruits as a way to project the reach of the caliphate. While the wilayats serve as outposts for recruiting, carrying out attacks and gaining territory, the foreign recruits can be used to export terrorism.
“Tackling ISIS affiliates around the world must start with weakening or eradicating the organization in Iraq and Syria first.”
Authorities believe that a cell of French and Belgian ISIS recruits carried out the November 2015 attacks in Paris that killed 130 people, as well as the March 2016 suicide bombings in Brussels that claimed at least 30 lives.
Most concerning, officials say, is that the Paris and Brussels attackers represent only a small fraction of foreign fighters that have left Europe to join ISIS. The International Center for Counter-Terrorism -- The Hague estimated in April that between 3,900 and 4,290 fighters had traveled from Western Europe to join ISIS or other groups in Iraq and Syria.
Fighters from Europe in Iraq and Syria
Germany:720 - 760
United Kingdom:700 - 760
Belgium:420 - 516
Sweden:250 - 300
Austria:230 - 300
Spain:120 - 139
The challenge authorities have had is tracking how many come back, and how many returnees are likely to carry out attacks. The Hague estimates that 30 percent of foreign fighters from Western Europe returned to their home countries, but it points out that "Not all foreign fighters are terrorists, and not all terrorists are foreign fighters."
European and Iraqi intelligence officials told the Associated Press following the Brussels attack that an estimated 400 to 600 ISIS fighters were trained specifically to carry out attacks in Europe.
ISIS has used its online magazine, Dabiq, to articulate the goal of "eliminating the grayzone" by using attacks to turn Western societies against their Muslim populations, thereby expanding the pool from which it can recruit.
Clint Watts, Fox Fellow at the Foreign Policy Research Institute, is skeptical of ISIS's capacity for such a "grand design." He says while European recruits may be driven by personal vengeance, for ISIS, such terrorist attacks are retaliation for Europe's bombing campaign in Iraq and Syria. Watts said these attacks also give ISIS a moment in the spotlight, even as it loses territory in Syria and Iraq.
"You can do five attacks in North Africa, and you get a fraction of the media coverage you get for 30 people in Brussels."
As with the expansion-through-affiliates strategy, it all comes back to increasing the sphere of ISIS's seeming influence, said Khatib of Chatham House.
"ISIS tells its followers around the world to engage in opportunistic attacks whenever and wherever they can," she said. "That's part of the drive to present the organization as having global influence."
It's also why, Khatib said, one key to stopping the expansion of ISIS is for the West and its allies in the Middle East to eliminate the impression that ISIS central is "seemingly robust."
"Tackling ISIS affiliates around the world must start with weakening or eradicating the organization in Iraq and Syria first."