Syrian militias armed by different parts of the U.S. war machine have begun to fight each other on the plains between the besieged city of Aleppo and the Turkish border. The fighting has intensified over the last two months, as CIA-armed units and Pentagon-armed ones have repeatedly shot at each other while maneuvering through contested territory on the northern outskirts of Aleppo. Last year, the Pentagon helped create a new military coalition, the Syrian Democratic Forces ... to take territory away from the Islamic State. The group is dominated by Kurdish outfits known as People's Protection Units or YPG. It has received air-drops of weapons and supplies and assistance from U.S. Special Forces. The U.S. backing for a heavily Kurdish armed force has been a point of tension with the Turkish government, which has a long history of crushing Kurdish rebellions. The CIA, meanwhile, has its own operations center inside Turkey from which it has been directing aid to rebel groups in Syria, providing them with TOW antitank missiles from Saudi Arabian weapons stockpiles. While the Pentagon's actions are part of an overt effort by the U.S. and its allies against Islamic State, the CIA's backing of militias is part of a separate covert U.S. effort aimed at keeping pressure on the Assad government. Over the last several months ... Kurdish-led groups [expanded] their zone of control to the outskirts of Aleppo, bringing them into more frequent conflict with the CIA-backed outfits.