The unlikely alliance between an offshoot of a leftist Kurdish organization and an Arab tribal militia in northern Iraq is a measure of the extent to which Islamic State has upended the regional order.
Across Iraq and Syria, new groups have emerged where old powers have waned, competing to claim fragments of territory from Islamic State and complicating the outlook when they win.
"Chaos sometimes produces unexpected things," said the head of the Arab tribal force, Abdulkhaleq al-Jarba. "After Daesh (Islamic State), the political map of the region has changed. There is a new reality and we are part of it."
In Nineveh province, this "new reality" was born in 2014 when official security forces failed to defend the Sinjar area against the Sunni Islamic State militants who purged its Yazidi population.
A Syrian affiliate of the Kurdistan Workers' Party (PKK) came to the rescue, which won the gratitude of Yazidis, and another local franchise called the Sinjar Resistance Units (YBS) was set up.
The mainly Kurdish secular group, which includes Yazidis, controls a pocket of territory in Sinjar and recently formed an alliance with a Sunni Arab militia drawn from the powerful Shammar tribe.