Islamists' harsh rule leaves scars

• The radical opposition group ISIS was driven from Addana more than a month ago


• Locals describe mass executions committed by the al Qaeda-influenced group


• A war within a war is taking place in Syria, pitting rebel fighters against radicals from ISIS


• The town is still reeling from the group's yearlong brutal reign

Addana, Syria (CNN) -- From the moment we cross the Turkish border into Syria, evidence of the Islamic State in Iraq and Syria's draconian and brutal rule lingers.

More than a month after the group was driven from the town of Addana, residents here drive through the streets, pointing out where ISIS fighters carried out executions and left bodies to rot for all to see.

"That's where they had one of their checkpoints," says rebel fighter Abu Sa'ed, pointing to a small concrete building on the side of the road as we speed past.

ISIS arrived in Addana about a year ago, initially welcomed in the conservative town by Islamist fighters. But within a few months, ISIS had entrenched itself and begun exerting its harsh order through what one fighter calls "terrorism and punishment."

The checkpoint at the entrance to the Syrian town of Addana is where members of the Islamic State in Iraq and Syria, or ISIS, used to dump the bodies of those they had executed to remind others of the consequences of violating their harsh rules. Now that ISIS has left the town, a flag representing the Islamic Front flies over the checkpoint.

ISIS moved into the conservative town about a year ago and was initially welcomed by rebels fighting the Syrian government. Once entrenched, ISIS began enforcing strict rules.

People shop and sell goods in the town center midday in Addana. Under ISIS rule, shops were forced to close for the noon prayers, and activities such as smoking were banned. Those who violated the rules were executed or just disappeared.

A young boy stands guard near what used to be an ISIS jail. This area that overlooks the town was used for training and executions.

Black paint, used by ISIS to mark its territory, can still be seen on the entrance to the jail area. ISIS painted many of the buildings in the town black to announce its presence, and the locals have recently repainted many of the buildings white.

This warehouse was used as a jail to hold and execute prisoners. A mass grave was found behind it, and bullet holes mark its walls.

Residents dig up the mass grave behind the jail in an effort to identify those killed and to bury them properly.

A shoe, a severed foot and several socks are uncovered at the grave site. This is significant to the residents because a missing man was last seen in the market buying socks for his family.

The bodies of three brothers were also discovered in the grave.

This man came to identify the bodies of his brothers. He knew two of them were dead, but he had hoped that one was still alive and being held elsewhere by ISIS.

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

ISIS reign of fear in Addana, Syria

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"ISIS came in and took over one area and announced it was an Islamic state and did whatever they wanted," Abu Sa'ed says.

In the passenger's seat, fellow fighter Abu Jaafar sighs, his AK-47 trained out the window.

"They used to leave the bodies of people they executed at the checkpoint for days," he says. "The corpses would rot. No one could avoid looking at them."

Amid the civil war in Syria, another war is taking place -- one that pits moderate and Islamist rebels against radicals from ISIS, a group so radical that even al Qaeda has reportedly distanced itself from it. Both groups of fighters are opposed to the government of Syrian President Bashar al-Assad.

For months, reports have been emerging from northern Syria about ISIS atrocities.

In Addana, bullet holes riddle the walls at a former ISIS prison. Most of them are at the same level -- the average height of a man.

"Those are mostly from the executions," says Abu Jamal, another fighter. "Others are from the battle."

At the town's courthouse, a fresh coat of white paint covers the black mark left by ISIS -- known to paint buildings black as they take over Syrian towns. Executions would take place out front. In the back, freshly dug dirt marks where some of the bodies were buried in mass graves.

Abu Jamal points to a pile of burning trash. ISIS beheaded one of the top rebel commanders -- placing his head in that very spot -- in broad daylight when the market was packed with people as a warning: anyone who dared oppose them would have the same fate.

In early January, rebel groups banded together and launched an offensive against ISIS in Addana and other areas in northern Syria.

"We had to leave the fronts with the regime," Abu Jamal says, "and fall back to fight ISIS and liberate the already liberated areas."

Still, many in Addana are too afraid to speak openly. So deep is their fear, they don't even want to be seen with us.

[ISIS] used to leave the bodies of people they executed at the checkpoint for days. The corpses would rot.

Abu Jaafar

Next to the former prison, a family waits, hoping for closure. Volunteers shovel dirt from a grave they dug up before. Video filmed at the time shows four contorted corpses. It's among many mass graves rebel fighters have unearthed.

"We found a foot, a shoe, and a jacket," Addana resident Ayoush Ali tells us.

Her neighbor Mohammed Ismail joins us. His two younger brothers are missing, he says.

"It's my brother's jacket. He just went out to get sugar and tomatoes."

A man drops a pile of children's socks, covered in dirt, on the ground.

"His wife wanted socks for their kids," Mohammed says, still disbelieving.

The day after we meet Mohammed, the bodies are dug up. It's three of his brothers who were killed by ISIS. He had thought one of them was in jail.

He crouches on the ground, covering his face, shoulders shaking as he sobs.

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