On Saturday night, five young Syrians slouched into a dive bar in New York and ordered drinks. When the bartender asked if off-brand vodka was O.K., they had to smile. They were all exiles from Raqqa, the provincial city in northern Syria that ISIS has made its operational center and the de-facto capital of the Islamic State. No one needed the good stuff. Just a drink would do.

Everyone in the group works for Raqqa Is Being Slaughtered Silently (R.B.S.S.), a kind of underground journalistic-activist enterprise that, under the threat of grisly execution, smuggles images and reports on ISIS from Raqqa to its allies abroad. The group’s comrades, in turn, post them on social media and its Web site. ISIS has controlled Raqqa for nearly two years and much of the foreign press looks to R.B.S.S. for firsthand reports about the daily life—and depredations—in Raqqa. And because they have dared to post reports of crucifixions, beheadings, sexual abuse, and other crimes, members of R.B.S.S., both inside the city and abroad, have been murdered by ISIS for their work.

Abdalaziz Alhamza, a slender man of twenty-four, acts as spokesperson. As recently as a few years ago, he was a biology student at Raqqa University who dreamed of studying pharmacology in Jordan or Turkey and returning home to start his career and a family.

“I was a normal guy,” he said, after taking a first sip of his vodka-and-Sprite. “I hung out with friends at cafés and bars. None of us were political. In Syria, before the revolution, it was a crime to be political in any way.” Raqqa was a relatively prosperous city with energy resources and an agricultural base. Major dams in the area are an important source of power in Syria.

When anti-regime demonstrations broke out in March, 2011, in Dara’a, a city in the south, and reports spread throughout Syria that Bashar al-Assad’s security forces were firing on civilians, Alhamza and many others joined in protests, in Raqqa. “We wanted to be free,” he said. “It seemed simple.”

As the uprising against Assad spread throughout Syria and the casualty counts rose, tens of thousands of people left Aleppo, Homs, Idlib, and other embattled cities and towns and arrived in Raqqa, which is on the northern bank of the Euphrates River. The city swelled and became known for a while as “the hotel of the revolution.”

By March, 2013, Free Syrian Army (F.S.A.) troops, as well as Islamist rebel forces, including al-Nusra, controlled the city and tore down a statue of Assad’s father, Hafez al-Assad, to celebrate. “Raqqa was the first liberated city in Syria,” Alhamza said.

But at around the same time, members of ISIS, or the Islamic State, bearing black flags, began accumulating in the nearby town of Slouk. “At first, there were only around fifteen people,” Alhamza said. “None of us knew about it” until fighters from al-Nusra began switching over to ISIS, which had its origin in Iraq. “Over time, around ninety per cent of the Nusra fighters in the area became ISIS, and only ten per cent of them refused,” Alhamza said.

In May, 2013, ISIS fighters started making kidnapping runs and attacking F.S.A. leaders, and, by late summer, there were full-scale battles with F.S.A. troops. As the F.S.A. began to suffer defeats, car bombings, kidnappings, and executions, one of the journalists at the table said, some F.S.A. soldiers “out of complete fear” also joined ISIS. People in Raqqa could see that ISIS was growing stronger, as they brought in heavy weapons from Iraq and seasoned soldiers who had fought in the Iraqi Army under Saddam Hussein. By the beginning of 2014, ISIS had absolute control of the city. They now overran the mosques, drove out Christians from the city, and turned major municipal buildings into their various headquarters. The propaganda campaign that ISIS mustered following the capture of Raqqa brought on a wave of foreigners.

“No one thought about the caliphate until 2014 when they declared Raqqa the capital of the caliphate and then these guys started coming in from all around the world,” one of the R.B.S.S. journalists told me. “It was like New York! A second New York! People from Australia! From Belgium! From Germany! From France! A global tide!”

“Maybe the next World Cup will be in Raqqa!” another of the journalists said, sarcastically.

The young foreign fighters were, and remain, privileged characters in the city. There are thousands of them in Raqqa, one of the R.B.S.S. journalists said: “When you are on the street you see them everywhere. They love fast-food places and Internet cafés. They love Nutella and they’ve got cans of Red Bull. Chocolates! Cheesecake! People are poor and see these expensive things! But ISIS wants to keep these Western recruits happy.”

The first crucifixion came early that spring—a horrific event to recall even now. Everyone at the table remembered the shock of it. Then came more: two people, shot in the head by ISIS executioners, crucified, and left for days for all to witness in the city’s main traffic roundabout.

“This was something new that we had never seen, this kind of violence,” Alhamza said. “They started cutting heads off, crucifixions. They spread panic everywhere.” There were edicts against drinking and smoking. Enforced by an all-female morality police called the Khansaa Brigade, women were made to wear the veil and, eventually, black shoes only. They are beaten if their niqab is somehow too revealing, a veil too flimsy, or if they are caught walking on the street alone.

“I can say that women are the people suffering the most under ISIS,” one R.B.S.S. member said. “They can’t show their faces. ISIS bothers them a lot. They take sticks and slash them on the street if the veil shows the eyes. They say, ‘Hey, hey, do you want to marry me?’ People have become so poor, the families so weak, that some give up their daughters to ISIS. They accept it. Sometimes ISIS forces them to do this. The Yazidis—ISIS says these people believe in Satan. And because of that their women are just traded from man to man in ISIS, sold, raped, abandoned.”

Schools were closed down. ISIS’s imams dominated the mosques. Many children were sent off to ISIS’s religious institutions, where they were taught the most fanatical form of the faith, and then to military camps, the R.B.S.S. activists said.

“Not everyone who joined ISIS did it because they believe the ideology,” Alhamza said. “I have a friend who is with ISIS but doesn’t like ISIS at all. … I called him and said, ‘Why did you join? You hate them!’ He said, ‘I am a doctor and they did not let me work. They told me, ‘If you wanted to work, you have to join us.’ I couldn’t live otherwise. I have children . . . ’ ”

In their recruiting, ISIS targets the local youth, according to members of R.B.S.S. With schools closed down, kids play aimlessly in the street. ISIS members befriend them, give them gifts, sometimes candy, sometimes a mobile phone. They ask the kids to join ISIS, one R.B.S.S. member said, “But they say, ‘Don’t tell your parents.’ I know about one child who went missing for months. His parents looked and looked. Thirteen years old, a boy. Finally, the father said to an ISIS leader, ‘Where is my son, I’ll give you money.’ Turns out the child was in a training camp for ISIS. They kidnap these children. They are sent to a mosque for education, so they are brainwashed with an extremist form of Islam. After this, they are sent to army camp to teach them how to fight, how to make and carry bombs. At their graduation, they have orders to execute someone––sometimes a beheading, sometimes they just cut off the head of a sheep.”