The group known variously as ISIL (Islamic State in Iraq and the Levant), ISIS (Islamic State in Iraq and Syria) or simply Islamic State is, originally, an offshoot of Al-Qaeda in Iraq. But while it shares a similar ideological outlook, ISIL has adopted a different strategy from its predecessor. What distinguishes the new armed group is its capture and occupation of swaths of territory, stretching from the outskirts of Aleppo, Syria’s largest city, eastward beyond Tikrit, Saddam Hussein’s war-torn hometown in Iraq.
ISIL has established what it calls a caliphate, with the northeastern Syrian city of Raqqa as its capital, and has imposed its harsh interpretation of Islamic law on areas under its control.
Whereas Al-Qaeda prioritized transnational attacks against the United States and its allies to galvanize support, ISIL’s leaders believe they can create a center of gravity for like-minded elements worldwide by building and defending a working quasi-state on the ground.
Although the population of areas under ISIL control is predominantly Sunni Arab, sprinkled throughout are minority groups that have lived for thousands of years in the Fertile Crescent.
Human rights groups have accused ISIL of ethnic cleansing and committing war crimes, such as public executions and recruiting child soldiers. Although the group has beheaded hundreds of local captives, the grisly videotaped execution of American journalists James Foley and Steven Sotloff and British aid worker David Haines attracted global attention. And the group still holds more than a dozen hostages.
Over the summer, ISIL made major gains in Iraq, seizing its second biggest city, Mosul, and threatened to overrun parts of the Kurdish regional government.
The failure of the Shia-led government of then–Prime Minister Nouri al-Maliki to incorporate Sunni interests was widely viewed by analysts as a key factor enabling ISIL’s gains. The U.S. hopes that replacing Maliki with the ostensibly more inclusive Haider al-Abadi — with the blessing of both Washington and Tehran — will convince more Sunni Iraqis to fight the group.
ISIL also made rapid gains in Syria late in the summer, attempting to break the grip of other rebel groups around Aleppo, which could deal a massive blow to the fight against Syrian President Bashar al-Assad.
The CIA estimates that ISIL is comprised of more than 30,000 fighters, of whom about half are foreign, including at least 2,000 who hold Western passports. The group’s success on the battlefield is believed to have significantly boosted international recruitment.
ISIL’s leader, Abu Bakr al-Baghdadi, is a veteran of the Sunni insurgency against U.S. troops in Iraq, and most of the senior military leaders are reportedly Iraqis who met in prison during the U.S. occupation. Many of its officers are veterans of Saddam Hussein’s Baath Party. Jordanians, Saudis, Tunisians and Chechens are well represented in the group's ranks, and its highly effective social media arm helps give the movement global reach.
Many governments are now trying to stop their nationals from joining the fight. But even if foreign arrivals have slowed, many aggrieved Sunnis across the region — especially in poor, rural areas — have heeded ISIL’s call.
ISIL’s ascent is partly a product of the group’s ability to fund itself through proceeds from captured oil fields, which generate up to $2 million from 50,000 barrels per day, while weapons, supplies and recruits pass easily across the border with Turkey.
Thomas Sanderson at the Center for Strategic and International Studies said financing sources include “refining, shipment, trade, granaries and sales of government equipment.” He added that revenue also comes from “kidnap for ransom, theft of antiquities, extortion from truckers and taxation of [6 million] local people.”
The CIA estimates that ISIL fields more than 30,000 fighters, of whom about half are foreign, including at least 2,000 who hold Western passports.
With a $2 billion war chest, the group pays fighters $400 per month — twice what other similar groups offer. ISIL is considered powerful and self-sufficient, hardly vulnerable to sanctions.
The downside of the substantial infrastructure and heavy weaponry captured by ISIL: the group is a more visible target for U.S. airpower than Al-Qaeda ever was.
And ISIL has many enemies in the region. In Syria, they include Assad’s regime, as well the various rebel formations grouped under such umbrellas as the Free Syrian Army, the Islamic Front and even Jabhat al-Nusra, the Syrian branch of Al-Qaeda.
The group’s emergence has benefited Assad because of ISIL efforts to defeat his enemies, and has deepened Western doubts about helping to topple Assad.
While ISIL may be isolated by neighboring governments, it has grown in a vacuum. U.S. officials have repeatedly insisted that the campaign against ISIL will be a protracted one, with no end in sight.