In the cities and towns across the desert plains of northeast Syria, the ultra-hardline al Qaeda offshoot Islamic State has insinuated itself into nearly every aspect of daily life.
The group famous for its beheadings, crucifixions and mass executions provides electricity and water, pays salaries, controls traffic, and runs nearly everything from bakeries and banks to schools, courts and mosques.
While its merciless battlefield tactics and its imposition of its austere vision of Islamic law have won the group headlines, residents say much of its power lies in its efficient and often deeply pragmatic ability to govern.
Syria's eastern province of Raqqa provides the best illustration of their methods. Members hold up the province as an example of life under the Islamic "caliphate" they hope will one day stretch from China to Europe.
In the provincial capital, a dust-blown city that was home to about a quarter of a million people before Syria's three-year-old war began, the group leaves almost no institution or public service outside of its control.
"Let us be honest, they are doing massive institutional work. It is impressive," one activist from Raqqa who now lives in a border town in Turkey told Reuters.
In interviews conducted remotely, residents, Islamic State fighters and even activists opposed to the group described how it had built up a structure similar to a modern government in less than a year under its chief, Abu Bakr al-Baghdadi.
Reuters journalists are unable to visit the area for security reasons.
The group's progress has alarmed regional and Western powers - last month US President Barack Obama called it a "cancer" that must be erased from the Middle East as US warplanes bombarded its positions in Iraq.
But Islamic State has embedded itself so thoroughly into the fabric of life in places like Raqqa that it will be all but impossible for US aircraft - let alone Iraqi, Syrian and Kurdish troops - to uproot them through force alone.
Last year, Raqqa became the first city to fall to the rebels fighting to overthrow President Bashar al-Assad. They called it the "Bride of the Revolution."
A variety of rebel groups ranging from hardline Islamists to religious moderates held sway in the city, although Islamists clearly dominated. Within a year, Islamic State had clawed its way into control, mercilessly eliminating rival insurgents.
Activists critical of the group were killed, disappeared, or escaped to Turkey.
Alcohol was banned. Shops closed by afternoon and streets were empty by nightfall. Communication with the outside world - including nearby cities and towns - was allowed only through the Islamic State media centre.
But after the initial crackdown, the group began setting up services and institutions - stating clearly that it intended to stay and use the area as a base in its quest to eradicate national boundaries and establish an Islamic "state".
"We are a state," one emir, or commander, in the province told Reuters. "Things are great here because we are ruling based on God's law."
Some Sunni Muslims who worked for Assad's government stayed on after they pledged allegiance to the group.
"The civilians who do not have any political affiliations have adjusted to the presence of Islamic State, because people got tired and exhausted, and also, to be honest, because they are doing institutional work in Raqqa," one Raqqa resident opposed to Islamic State told Reuters.
Since then, the group "has restored and restructured all the institutions that are related to services," including a consumer protection office and the civil judiciary, the resident said.