Across the broad swath of territory they control bridging Syria and Iraq, extremist militants from the group known as the Islamic State have proven to be highly organized administrators. Flush with cash, they fix roads, police traffic, administer courts, and have even set up an export system of smuggled crude from oil fields they have seized.
But the extremists — a mix of Iraqis and Syrians but also foreign fighters from Arab countries and non-Arab regions like the Caucasus — run the risk of provoking a backlash from the people they have come to rule.
Unlike Lebanon's Hezbollah or the Palestinian militant group Hamas, which have deep roots in their communities, the Islamic State group is not a grassroots movement and its sway over its populations is ultimately based on violence, not necessarily a groundswell of support for its vision of a hard-line Islamic caliphate. While it has been welcomed by some disenfranchised Iraqi Sunnis as potential saviors from the Shiite-dominated government in Baghdad, many consider the group an alien entity.
In recognition of that, the group has varied the imposition of the radical version of Islamic law they advocate. In their main stronghold in Syria, the city of Raqqa, they have unleashed it without reserve, killing perceived offenders and cutting off the hands of thieves in public.
But in Iraq's second largest city, Mosul, they have been more cautious. They've taken some steps like banning alcohol and painting over street advertisements that show women's faces — but have held off on strict punishments.
The Iraqi city of Duluiyah is a prime example of the possibility for overreach.
Weeks ago, a small group of Islamic State fighters and other insurgents entered the Sunni-majority city just north of Baghdad and were welcomed by residents, said one resident, Jassim Mohammed. But within days, the Islamic State fighters came with lists of "wanted" men, including police officers and local businessmen.
That prompted an uprising by residents who forced the militants out, leaving the town under control of Sunni tribesmen, Mohammed said.
On Sunday, Islamic State fighters stormed back into Duluiyah, seizing the mayor's office, police station, local council and courthouse.
There has also been less dramatic pushback. In Mosul, the militants offered three local figures the post of governor of Ninevah— the province of which Mosul is the capital — and each refused, said Laith, a civil servant in the city who asked to be identified only by his first name for his own safety.
"People are worried that the (Iraqi) government might come back and that they would be punished for dealing with the Islamic State," he said.
The leader of the Islamic State group appears to recognize that over the long-term his fighters are not governors. In an address after the June 9 fall of Mosul, Abu Bakr al-Baghdadi appealed to Muslims around the world with practical skills — scholars, judges, doctors, engineers and administrators — to flock to the regions his group controls to help build the state.
Over the past month, the group has consolidated its hold over an impressive stretch of territory, roughly 700 kilometers (435 miles) from end to end. From its western-most end on the outskirts of the Syrian city of Aleppo, it stretches across northern Syria and most of the east then bridges into most Sunni-dominated areas of northern and western Iraq up to the edges of Baghdad.