1. The Islamic State in Iraq and Syria, known as ISIS, took over the Iraqi city of Mosul this week, raising fears from Baghdad to Washington that the group could achieve its deadly aim: to create its own ultra-violent state starting in Iraq and Syria.
ISIS’s territorial control — while precarious in some parts — now expands from the city of Raqaa in eastern Syria to Mosul and Tikrit in western Iraq.
2. ISIS formed as an al-Qaeda offshoot a decade ago following the controversial U.S.-led invasion of Iraq, and the bloody Sunni insurgency and destabilizing civil war that followed.
At the time, it was known by a few names, including the Islamic State in Iraq, or ISI.
3. ISIS resurged after the Syrian conflict started to escalate in 2011. Under the guidance of Abu Bakr al-Baghdadi (once a top al-Qaeda leader in Iraq), the group changed names to the Islamic State in Iraq and Sham (Arabic for “greater Syria”).
The Sham in ISIS’s name is sometimes translated as Levant (hence ISIL).
4. ISIS is fighting for an Islamist state in Iraq and Syria. The two countries were designated as distinct states by the 1916 Sykes-Picot agreement between Britain and France, which drew largely arbitrary national borders in the Middle East.
Iraqi policemen stand guard at a checkpoint in Baghdad, Iraq.
7. In Syria, ISIS quickly gained ground, attracting other rebels with its reputation as being among the most fearsome and most fundamentalist. ISIS conquered the eastern Syrian city of Raqaa in 2013 and claimed it as the capital of its expanding “state.”
8. But ISIS’s ultra-violent tactics against civilians and other rebels — from public beheadings to crucifixions for violations of its religious interpretations — have also alienated many Syrians and rebel allies, al-Qaeda included.
People demonstrate outside ISIS offices demanding they stop fighting with the rebels in January.
9. In February, al-Qaeda’s official proxy in Syria, the al-Nusra Front, joined forces with other Syrian rebels to oust ISIS. The campaign was initially somewhat successful, but in the months since ISIS has kept expanding.
In May, al-Qaeda’s leader Ayman al-Zawihiri officially cut off all ties with ISIS.
10. At the same time in Iraq, ISIS has preyed off long-simmering political instability to gain control of Anbar province in the west. Unlike in Syria, ISIS in Iraq draws significant local support from groups angry with the Iraqi government and police.
ISIS fighters with suspected Iraqi soldiers.
11. Many Iraqis, particularly Sunnis, accuse the Shia-dominated Iraqi government and security forces of widespread corruption and abuse. Many are disillusioned with Prime Minister Nuri al-Maliki’s increasingly authoritarian and sectarian rule.
Iraqi security forces arrest suspected ISIS militants.
13. But in January, ISIS seized control of Fallujah and much of nearby Ramadi near Syria’s border. Fallujah was the center of the Sunni insurgency against the U.S.; the city’s capture was a significant tactical and symbolic defeat for the Iraqi government.
Back in December, the Iraqi government angered many in Anbar after security forces violently broke up a Sunni-led protest camp accused of providing cover for al-Qaeda.
14. Over the next six months, ISIS continued to terrorize Iraqi troops and form alliances with tribes and local militias, many of whom had been aligned with Saddam Hussein’s Baath party and the Sunni insurgency during the U.S. occupation.
16. After months of small battles, on June 10, ISIS seized control of Mosul, Iraq’s second largest city. Iraq’s poorly trained and resourced soldiers abandoned the city — and their U.S. tanks and weapons — to the invading militants.
ISIS militants quickly took over the city’s airports, banks, jailed, and government institutions.
17. ISIS’s seizure of Mosul ignited panic around Iraq; an estimated 500,000 Iraqis fled Mosul and its environs fearing that the fighting would escalate further. Many headed west to Iraq’s autonomous Kurdish region, considered the region’s safest place.
18. The Iraqi army’s quick retreat from Mosul raised some red flags. About 300 Iraqi soldiers a day were already deserting the military because of poor pay and safety concerns, according to the New York Times.
The U.S. has spent around $14 billion to train and secure the Iraqi security forces.
19. On Wednesday, ISIS fighters continued to advance and seized Tikrit and surrounding towns. Images of ISIS with U.S. tanks in Iraq and Syria sent shock waves worldwide. On Thursday, Kurdish fighters took control of Kirkuk to ward off ISIS’s advance.
20. Official Iraqi response has been tepid: On Thursday parliament met, but failed to reach the necessary quorum to declare a state of emergency. Meanwhile, Maliki has urged Iraqis to sign up for the army and encouraged public displays against insurgents.
Many fear that Maliki would use the excuse of emergency rule to bolster his heavy-handedness.