These men are no longer just on the frontlines in the Syrian war. They are establishing a presence in villages, particularly those that lie along the main routes to the Turkish border. And in these villages they are laying the foundations for a future state.
They don't hide what their aim is: creating an Islamic state under Sharia.
We came into contact with the Islamic State in Iraq and the Levant, al-Qaeda's branch in Syria, at one of their checkpoints in the village of Dar Ta Izza in Allepo province.
They didn't want to let us pass without checking our identities. One of the fighters said that the "regime thugs working in the Free Syrian Army (FSA)" are trying to smuggle "wanted people".
After checking our identities, they escorted us to their leadership in the nearby village of Dana where there were deadly clashes between the Islamic State and units linked to the Free Syrian Army.
"You are our guests ... Don't worry," was what a young fighter from Tunisia told me when he got into our car.
I told him that we are interested to hear the view of the Islamic State in Iraq on the circumstances behind the violence in Dana. It wasn't the first incident of its kind whereby local Syrian armed groups and Islamists engaged in clashes. They have become more frequent as of late.
"Why should we speak to the media? No one believes us anyway," the Tunisian fighter told me. "And the media is so biased against us. But anyway we are taking you to our commanders and they will decide what to do."
We arrived in Dana and it was clear ... The village was now under the control of the Islamic State. Scores of armed and masked men were patrolling the streets.
Armed opposition groups linked to the Free Syria Army were no longer there. They were forced to leave.
There was a gun battle during a demonstration against these foreign fighters. We cannot independently confirm who fired the first shot.
But Abu Osama al Tunisi says his men came under attack. He is the Emir of Dana - a title given to commanders in al-Qaeda's organisation. He is also a Tunisian.
Abu Osama showed us arrest warrants issued by the Islamic court in Idlib against those he said were responsible for arming the protesters.
"These groups were responsible for bringing the people ... who are government thugs and drug dealers onto the streets," Abu Osama.
"They are accused of corruption and refused to appear in court because they didn't recognise its legitimacy. So the court said force can be used to make the arrests. So we destroyed the sleeper cells.
"We say to those who want to harm or destroy the Islamic State ... It will become stronger."
And to become stronger you need the support of the people. We watched as they reached out to the villagers.
"I ordered my men to stay in their barracks to avoid any confrontation with the protesters," Abu Osama told people who gathered around him, and his armed men in the market.
"We were in our bases when they killed our bothers. We gave orders to our men not to leave our bases," he said.
"Did you see what they did to the Quran in the school when they ransacked it. Are they Muslims? I can give you a list of names who were invoked in the protests.
"They see members of sleeper cells who work for the government. Not one good person took part in the demonstration. They are bad. They don't oppose us but Islam. They don't want Islam. They had arms to kill Muslims."
A villager responded: "The protesters said they wanted to demonstrate against you Abu Osama. They said you were you were executing orders on behalf of God. They believe God didn't command you to cut people's hands off."
The conversation then ended.
At the start of the Syria war, many Syrians welcomed the help of foreign fighters who came from Islamic countries to support the fight against the Syrian regime.
It has been clear for some time now that these these fighters from the Islamic State in Iraq and Levant hope to achieve one goal: They want to create an Islamic state. But not all in the Syrian opposition share that goal. And this has caused tensions.
The group has been criticised by some for its strict interpretations of Islamic law and punishments, including beheadings.
The Islamic State in Iraq and Syria's rank and file is mainly made up of foreigners. They are cementing their power in opposition-controlled territories. But the Islamic state says it is working to cleanse the area from regime supporters and those who are fighting Islam.
And we asked its vali - or governor of Allepo province, Abu Atheer - why some accuse them of trying to weaken Syrian opposition groups by taking control over border villages.
He didn't want to be filmed. But he told us: if we wanted to cut the supply lines it is easier for us to take the warehouses of the FSA. Anyhow we are buying weapons from the FSA. we bought 200 anti-aircraft missiles and Koncourse anti tank weapons. We have good relations with our brothers in the FSA. For us, the infidels are those who cooperate with the West to fight Islam.
If confirmed, purchasing weapons from the Free Syria Army won't be good news for the West.
It is men like these the West doesn't want to arm and it has urged the FSA to retake areas under their control. It could be a recipe for yet another war within a war that will decide the new face of Syria.