ERBIL, Iraq — In northern Syria, the jihadists of the Islamic State have fixed power lines, dug sewage systems and painted sidewalks. In Raqqa, they search markets and slaughterhouses for expired food and sick animals. Farther south, in Deir al-Zour, they have imposed taxes on farmers and shopkeepers and fined men for wearing short beards.
The group runs regular buses across the border with Iraq to Mosul, where it publicly kills captives and trains children for guerrilla war. Last month, it reopened a luxury hotel in the city and offered three free nights to newlyweds, meals included.
A year after the Islamic State seized Mosul, and 10 months after the United States and its allies began a campaign of airstrikes against it, the jihadist group continues to dig in, stitching itself deeper into the fabric of the communities it controls.
In vast areas of Syria and Iraq with shattered ties to national governments, the jihadists have worked to fill the void, according to interviews with residents from areas in Syria and Iraq ruled by the Islamic State, also known as ISIS or ISIL. The group is offering reliable, if harsh, security; providing jobs in decimated economies; and projecting a rare sense of order in a region overwhelmed by conflict.
With no political solutions in sight for the wars that have allowed the group to thrive, little has prevented the jihadists from deepening their roots in ways that will make them even harder to dislodge.
“As a way of life, people got used to it,” said a laborer from Raqqa who had earned good money painting the group’s new offices in the city.
If you followed the rules, the jihadists left you alone, he said, although he wished life were more peaceful.
“It is not our life, all the violence and fighting and death,” he said, speaking on the condition of anonymity, like others from areas run by the Islamic State, so as not to anger the jihadists. “But they got rid of the tyranny of the Arab rulers.”
In the process, the Islamic State’s administration has ballooned. The group has issued declarations banning dynamite fishing and Apple products, pressuring teachers to work in its schools, offering rewards for the killing of Jordanian fighter pilots and advising wounded residents not to travel to Turkey for prosthetic limbs because the Islamic State now makes them at home, according to jihadist documents compiled by Aymenn Jawad Al-Tamimi, a fellow at the Middle East Forum.
The Islamic State’s territory now stretches across hundreds of miles, from the outskirts of Aleppo in Syria into central Iraq, where it shares a volatile border with the Kurds in the north and approaches Baghdad in the south. Much of that area is sparsely populated desert, but the group has millions of people under its charge, as well as archaeological sites, a hydroelectricdam and oil fields that help finance its operations.
The Islamic State differs from jihadist groups like Al Qaeda in its drive to establish a Sunni Muslim state governed by an extreme version of Islam.
Its method of seizing territory seeks to lay the groundwork for this by prompting a “geographic cleansing,” according to Hassan Abu Hanieh, a Jordanian expert on Islamist groups. Enemies — like government soldiers, the police and those who do not fit in, such as minorities or elites — flee or are killed. What remains are mostly Sunni Arabs who try to continue their lives with little disruption.
The Islamic State works to co-opt them through the “management of chaos,” providing services otherwise lacking in wartime, Mr. Abu Hanieh said. “People may not be with the organization’s ideology, but the group has been able to give some stability, punish thieves and put in place a legal system,” he said. “In general, the normal people want no more than that.”
Many residents have become dependent on the Islamic State’s services, Mr. Tamimi said.
“The end effect of this is that the Islamic State entrenches itself and becomes very difficult to get rid of,” he said. “Are you going to bomb the schools in the towns they run and deny the people access to any education whatsoever?”
To enhance their staying power, the jihadists have focused on children, revamping curriculums and indoctrinating teachers.
Islamic State propaganda videos released online often show children planting bombs to kill Iraqi security forces, cheering for Islamic State convoys and watching executions. One recent video showed young boys in black masks learning to fight, do an army crawl and carry out ambushes with automatic weapons.
“The biggest threat we have is that the children have a new curriculum that is very extremist,” said a Kurdish security official who monitors the Islamic State from northern Iraq. “This is a ticking time bomb for the future.”
That worries parents in Islamic State areas.
One former real estate agent said that even though he hated the jihadists, he had managed to survive the changes in Raqqa. He tore the stereo out of his car so the jihadists could not accuse him of listening to forbidden music, but he still does so at home, quietly. He buys cigarettes from smugglers who sell only to people they know, since jihadists punish smoking as a crime.
“This is like heroin for them,” the real estate agent said, enjoying a pack during a recent trip to Turkey.
He does not criticize the jihadists at home for fear that his 8-year-old son will repeat what he says in public, endangering the family. But his son hears things elsewhere, he said, “and now sometimes I hear him defendingISIS.”
Some adults said living under the Islamic State had changed their views. “If you had asked me before the revolution, I would have said I wanted to be the richest person, with houses and cars,” another Raqqa resident said. “But after we sat with their religious teachers, we changed our way of thinking.”
He was considering whether to join the group, he said, and knew he would marry and raise his children in Raqqa so they could learn “the true religion.”
The dynamics of Islamic State rule differ from place to place. In Mosul, food is plentiful, but the jihadists restrict people who try to leave the city, making relatives vouch for them and arresting the family members if the travelers do not return.
Life is easier in Raqqa, where residents regularly cross the Turkish border, returning with goods and cash earned outside.
Locals suffer more around Deir al-Zour, where the Islamic State fought for nearly a year to subdue local tribes and rebel groups in battles that killed more than 1,000 people.
Bad blood from the fighting persists, and Islamic State fighters are still ambushed regularly, activists said. The Islamic State has responded with public executions and heavy taxes on harvests, phone lines, water and electricity.
“Their policy is to make people hungry while they pay their fighters so that becoming one of them is the only way to live and eat,” one activist said.
An activist with the group DeirEzzor24 said one of his cousins had joined the Islamic State, earning $100 per month, plus $100 for his parents and $40 each for his siblings, a strategy aimed at winning over the whole family.
In an audio message released last month, the leader of the Islamic State, Abu Bakr al-Baghdadi, renewed his call for Muslims to join the group. He said those outside it were “homeless” and “humiliated,” while Islamic State residents lived “with might and honor, secure by God’s bounty alone.”
Residents of Islamic State areas did not describe easy lives, but some wanted the jihadists to stay, reflecting the deep political failures in their countries.
Many now living under the Islamic State in Syria suffered under both President Bashar al-Assad and the rebels who chased out his forces, leaving them with no alternative to the jihadists.
And many Sunnis in Iraq trust the Islamic State more than the Shiite-led government in Baghdad and the militias it has used to fight the jihadists.
“Now there is more security and freedom, no arrests, no harassment, no concrete barriers and no checkpoints where we used to spend hours to get into the city,” said Mohamed al-Dulaimi of the jihadist-controlled city of Falluja, Iraq.
“What will happen if the militias enter Falluja?” he asked. “We will take our guns and fight them, not because we are ISIS, but because the militias will kill us all.”