The Euphrates

Aleppo: Ejected by Other Rebel Groups In 2013, ISIS emerged from the remnants of Al Qaeda in Iraq and began to operate in Syria. The vacuum created by the country’s civil war provided a place for ISIS to rebuild. Syrian rebel groups initially welcomed ISIS as an ally, but soon realized that they did not have the same goals. ISIS was more interested in forming an Islamic state than in toppling the Syrian government — and had no problem with killing other insurgents to make it happen. These tensions culminated in a revolt against ISIS. The group was driven out of Aleppo, Syria's largest city, in January by the other rebel groups.

Jarablous: Supply Routes ISIS Control After being pushed out of Aleppo, ISIS moved east, attacking rebel bases and taking over towns like this one, near the border with Turkey, that are arteries for money and supplies.

Deir Hafir: Cutthroat Tactics ISIS Control ISIS has inspired a new generation of jihadists with its emphasis on creating an Islamic state and its willingness to kill Shiites and even rival Sunnis, like when it recently crucified eight rebel fighters in the town square here for being too moderate. Al Qaeda, which has preached against the wanton spilling of Muslim blood, severed ties to ISIS in February and has condemned its tactics.

Maskana: Terror Through Social Media ISIS Control ISIS may practice a seventh-century version of Islam, but its public outreach is thoroughly modern . It has used Facebook as a death-threat generator; the text-sharing app JustPaste to upload book-length tirades; and YouTube and Twitter to post gruesome videos and photos to terrify its enemies (reportedly live-tweeting the amputation of a man's hand in this town, for example).

Tabqa Dam: Seizing Infrastructure ISIS Control In addition to targeting cities and towns, ISIS has also sought control of major pieces of infrastructure, including dams, oil fields and a refinery. In some cases, like here at the Tabqa Dam, the group has negotiated with the workers at the facilities to keep them running. Built more than 40 years ago with Russian help, this dam provides electricity to a large part of Syria, including areas under ISIS’s control.

Raqqa: Instituting Strict Rules ISIS Control Via Associated Press In keeping with its goal of creating an Islamic state, ISIS has instituted strict rules in most of the towns it has seized. In this city, which was the provincial capital and is now ISIS's de facto capital, smoking and music are banned, women must cover their faces and shops must close at prayer time. The punishment for not complying: execution in the main square.

Deir al-Zour: Besieging a Provincial Capital Attacked by ISIS Ahmad Aboud/Agence France-Presse — Getty Images While ISIS holds sway over much of the oil-rich province of which this city is the capital, control of the capital itself has been split among other rebel groups and the Syrian government. ISIS took control of a bridge leading into the city, creating a partial blockade.

Abu Kamal: Erasing the Syria-Iraq Border ISIS Control ISIS seized the Syrian side of this border crossing on June 30 after brutal clashes with a Syrian insurgent group. Now, with both sides of the crossing under its control, ISIS can move men and supplies easily between Iraq and Syria. It is also another step closer to achieving its goal of creating an Islamic state across the two countries.

Qaim: Iraqi Forces Flee Border Post ISIS Control ISIS took control of this crossing on June 22 after Iraqi troops, sent to reinforce the border, fled. Members of that unit said they were eager to fight but that their commanders failed to provide them with water and food , causing them to abandon their positions.

Rawa: Without a Fight ISIS Control ISIS captured this town and neighboring Ana after Iraqi troops fled, though a government spokesman said the security forces withdrew as a “tactical” move to reinforce troops in other areas.

Haditha Dam: Concerns About Sabotage With the nearby towns of Rawa and Ana under ISIS control, officials are concerned that the group could capture Haditha Dam , Iraq’s second-largest, and wreak havoc. When ISIS fighters seized the Falluja Dam in April, they opened it, flooding crops as far as 100 miles south. The water washed east as well, reaching Abu Ghraib, near Baghdad. On the other hand, ISIS fighters have been in control of the Tabqa Dam in Syria for months without major incident.

Ramadi: The Government Provides an Opening for ISIS ISIS Control Tensions between this city’s residents, who are mostly Sunni, and the central government had been brewing here for at least a year. Then in December, Iraq’s prime minister, Nuri Kamal al-Maliki, ordered security forces to dismantle a protest camp — an outlet for disenchanted Sunnis angered at their treatment by the Shiite-dominated government. The action ignited days of violence and created the opening ISIS needed to seize parts of the city, the provincial capital.

Falluja: A Symbolic Fall ISIS Control Mohammed Jalil/European Pressphoto Agency Just days after the raid on the camp in Ramadi, ISIS fighters destroyed the Police Headquarters and mayor’s office here , planted their flag on government buildings and decreed the city to be theirs. Ten years earlier, American forces had captured this city from Qaeda-style insurgents at a considerable cost of American lives.

Abu Ghraib: Escapees Fuel Insurgency ISIS received an influx of recruits after a prison break in July 2013 at the detention center here. The escapees, who were imprisoned by the Maliki government or during the American occupation, are now among ISIS's leaders and foot soldiers. The group also attracts militants from around the world. Its recruits are better paid, better trained and better armed than other rebel groups and even the national armies of Syria and Iraq, according to leaders of rival factions.