The takeover of at least three of Iraq's biggest cities by a well-organized group of Sunni extremists not only poses the threat of civil war but could destabilize the entire region, say Middle East analysts.
"It's like the beginning of an earthquake," says Henry Habib, professor emeritus of political science at Concordia University.
Habib says the recent fall of Mosul and now Tikrit to the group the Islamic State of Iraq and Syria (ISIS) has the potential to fuel Islamist uprisings in Jordan and even Turkey.
It is also possible, some analysts say, that continued ISIS success could draw Shia Iran's Revolutionary Guards into the fray, which could add a much larger sectarian and regional dimension to the fight.
Meanwhile, taking advantage of the confusion, ethnic Kurds in northern Iraq swept in to control Kirkuk, one of the country's main oil hubs and the centre of much of its wealth.
On Wednesday, ISIS fighters swept into Tikrit, the birthplace and one-time Sunni stronghold of former Iraqi dictator Saddam Hussein, a day after capturing Mosul, a city of nearly two million residents in northern Iraq.
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The Guardian newspaper reported that fighters ransacked the main army base in Mosul and released hundreds of prisoners from jails. They also reportedly liberated hundreds of millions of dollars from banks in the region, Reuters reported.
Meanwhile the onslaught prompted half a million residents, as well as a reported 30,000 Iraqi soldiers, to flee the city.
On Thursday, several media sources reported that ISIS was advancing toward Baghdad, and were within 90 kilometres of the capital. The group released a statement saying, "The battle is not yet raging, but it will rage in Baghdad and Karbala" in the southwest.
Overnight Friday, ISIS pushed into the ethnically mixed province of Diyala, northeast of Baghdad, capturing two towns there. Police officials told The Associated Press that the Iraqi soldiers stationed in Diyala abandoned their posts without any resistance.
Occupies significant territory
Both Iraqi officials and Western observers have expressed shock at the speed with which ISIS, an offshoot of al-Qaeda, has been able to commandeer significant parts of the country.
ISIS has only been on the international radar for about a year, says Habib, but the group has been one of the more active anti-government militias in the Syrian civil war, and now occupies a significant swath of land — roughly the size of Switzerland — that stretches from the eastern fringe of Aleppo in northern Syria to Falluja in southern Iraq, which the group took earlier this year, to Mosul in the north.
Much of the group's success thus far is due to the intimidating effect of its fearsome reputation, says Habib. The group has not only kidnapped, tortured, bombed and executed opponents, it has also killed fellow jihadists who questioned its tactics.
"I see no reason to hold out hope that they have any moderation at all in their thinking or their actions," says Michael O'Hanlon, director of foreign policy research at the Brookings Institute, a think tank based in Washington, D.C.
ISIS is a successor to al-Qaeda in Iraq, the group headed by the late Abu Musab al-Zarqawi that arose in response to the U.S. invasion of Iraq in 2003, says Kamran Bokhari, vice-president of Middle Eastern and South Asian affairs for the geopolitical intelligence firm Stratfor.
He says ISIS's long-term aim is to establish a caliphate, or Islamic state, in Sunni-held areas of Iraq and Syria.
Led by a fighter known as Abu Bakr al-Baghdadi, ISIS was formed in Iraq, but it gained significant experience and clout fighting in the Syrian civil war against the Shia-backed regime of Bashar al-Assad, a conflict that has become a focal point for many international jihadis.
Break with al-Qaeda
While in Syria, al-Baghdadi reportedly had a falling-out with Ayman al-Zawahiri, the head of al-Qaeda worldwide, who wanted ISIS to cede its role in Syria to homegrown militants Jabhat al-Nusra, and focus its activities in Iraq.
Al-Baghdadi was having none of it, Bokhari says.
"Essentially, Baghdadi told Zawahiri, 'I don't report to you. You're not my boss. I'm my own man, I run my own, independent group,'" says Bokhari, co-author of the recent book Political Islam in the Age of Democratization.
Nonetheless, while the group managed to capture a significant stretch of land in eastern Syria, it realized it couldn't sustain a battle with both the Assad regime and rival rebel groups, and so decided to redouble its efforts in Iraq, says Bokhari.
The taking of Falluja, Mosul and now Tikrit has done a great deal to burnish ISIS's reputation.
Al-Baghdadi and his group have "become a magnet for a lot of jihadists around the world," says Bokhari, "because he's been able to prove himself on the battlefield, whereas Zawahiri has for many years done nothing more than issue videotapes."
Bokhari says that as a result of its recent gains ISIS "is in many ways the largest jihadist entity on the planet, because it can actually boast territory, whereas the old al-Qaeda is weakened and in hiding."
One of the reasons for ISIS's successes in Iraq is that it has been able to capitalize on the discontentment of minority Sunnis with the largely Shia-led government of Prime Minister Nouri al-Maliki.
Al-Maliki was elected in 2006 after the U.S. helped depose Saddam Hussein, but the Iraqi prime minister has only exacerbated sectarian divisions in this Shia-majority country, says Noomane Raboudi, a political science professor at the University of Ottawa with a specialization in the Middle East.
With the threat of ISIS on Baghdad's doorstep, al-Maliki has called on people to join the army and defend the capital.
'Swimming in money'
It is difficult to ascertain how big ISIS is in terms of membership — some sources maintain it has between 10,000 and 15,000 fighters.
The reason such a relatively small group was able to commandeer a large city such as Mosul is that ISIS is extremely well-armed and organized, says Habib.
"It's no longer a rebel group — it's a military organization," he says, and one that seems to be "swimming in money."
Raboudi says ISIS's main financial backers are likely religious groups in Gulf states such as Saudi Arabia and Qatar that may have previously supported al-Qaeda.
The group's military victories are also proving lucrative. The International Business Times reported that ISIS managed to loot about $429 million US from banks in Mosul.
If ISIS can manage to hold on to Mosul and Tikrit, and continue to accumulate cash through donations or the spoils of war, analysts say it's conceivable the group could make inroads into Jordan, Lebanon and possibly even Turkey.
"Turkey now has fires raging on two of its southern borders, Syria and Iraq, and they've got two enemies to deal with — the separatists Kurds and jihadists," says Bokhtari. "So the Turks cannot be oblivious to what's going on."
The Islamic State of Iraq and Syria (ISIS) is also commonly referred to as The Islamic State of Iraq and the Levant (ISIL). The acronym's last letter is open to interpretation because the last word in Arabic, "al-Sham," can mean the Levant, Syria or even Damascus in some instances.Jun 13, 2014 4:08 AM ET