A strategic crossing into Turkey from Syria may soon be in the hands of al-Qaeda after infighting among Syrian rebels broke out into open warfare. The assault on Azaz did not come from rebels against the Bashar al-Assad regime, but from al-Qaeda in Iraq and the Nusra Front against the Free Syrian Army, which had previously held Azaz:

Al-Qaeda-linked militants seized a key northern Syrian town from rebels on Wednesday, as mounting friction between anti-­government extremists and more moderate, Western-backed opposition factions erupted into all-out conflict.

The town of Azaz, two miles from the Turkish border, was overrun by fighters from the Islamic State of Iraq and the Levant after clashes broke out at the main hospital there. The fighting began when the al-Qaeda-linked group attempted to detain a German doctor, according to medics and activists.

The fall of the town, which lies on the road between the border crossing of Bab Salameh and the northern city of Aleppo, has the potential to disrupt rebel supply lines. The crossing itself, one of the few between Syria and Turkey that are still functional, remained in the hands of the more moderate Free Syrian Army on Wednesday night, despite reports that Islamic State was mounting an offensive to take it.

Although both mainstream opposition forces and al-Qaeda-linked fighters are battling the government of President Bashar al-Assad, the extremists have focused their energies lately on attacking their fellow rebels. Tensions between Islamic State and other rebel factions have been building since the group emerged on the ground earlier this year. It declared war on two mainstream rebel groups last week in what it labeled operation “cleansing evil.”

That complicates matters for the West, which used Azaz as both a conduit for aid and as an example of the effectiveness and moderation of the FSA. CNN reminds readers that John McCain used the Bab el Salama gate for his visit to Syria in his attempt to raise support for American intervention on FSA’s behalf.

The FSA expressed indignation over the lack of Western assistance against ISIS and Jabhat al-Nusra, which they now call “infidels.” However, the FSA itself admits that they let the radical Islamists into the fight themselves, as one FSA leader called for vengeance on CNN:

“[ISIS] are not rebels anymore; from this point, they are terrorists now,” said Louay Almokdad, the political and media coordinator for the FSA, said in an interview broadcast live on CNN.

“We are fighting two terrorist teams on two fronts; one al-Assad regime and Hezbollah militia and the Iranian revolutionary guards and the other the extremists al Qaeda, ISIS,” Almokdad added.

Until recently, there had been cooperation between the two groups. …

“These guys (ISIS) are infidels. They killed my brother and wounded my other brother,” said Hajouleh’s older brother, Khaled, who wept as he spoke to CNN.

The elder Hajouleh said he had previously helped facilitate the arrival of foreign jihadist fighters from Turkey, some of whom volunteered to fight with the hardline ISIS militia in Syria.

“I let these guys in, and I totally regret it,” said Khaled Hajouleh. “I thought these guys were coming to help us and protect us.”

Hajouleh’s brother coordinated media visits to Syria on behalf of the FSA, again to bolster global support for arming the rebels in Syria.  It seems very difficult to believe that they could have been that naive about the intentions of ISIS and the Nusra Front, given those groups’ publicly-stated goals of establishing a pan-Muslim caliphate based on shari’a law rather than the democracy promised by FSA leader Louay Almokdad in the video above.  They probably calculated that they could use the extremists as cannon fodder while retaining control of the rebellion, which turned out to be a massive miscalculation — and a good argument for refraining from sending the FSA anything that later can shoot back at us.