[2][3][10] When ISIL invaded the Sinjar Mountains in 2014 and began to massacre its Yezidi population, the PKK intervened with hundreds of fighters in order to save the locals from the Islamic State militants.

In late 2015, anti-ISIL forces finally succeeded in driving the Islamic State mostly from the Sinjar area, but the PKK fighters have since refused to leave and continue to train and equip the local PKK-affiliated militias.

Both sides later accused each other of having initiated the battle: Whereas the YBŞ said that they had peacefully asked the KNC fighters to leave the town, whereupon the latter attacked them with heavy weapons,[2] the Rojava Peshmerga stated that they were first shot at and decided to take a stand rather than simply retreat.

[13][14] In Rojava, the Kurdish youth group Ciwanen Soresger, which is close to the PKK-allied Democratic Union Party, attacked KNC offices in Al-Darbasiyah and Qamishli in protest of the Sinjar clashes.

Josef Weidenholzer, a Member of the European Parliament and chairman of the Yezidi Friendship Group, appealed the Rojava Peshmerga and the Sinjar Resistance Units to "stop all hostilities and solve political differences", also because any international support to either faction is dependent of "the peaceful solution of Intra-Kurdish problems".

[2] An expert also warned that both the Sinjar Resistance Units as well as the Rojava Peshmerga had been very effective at "keeping IS at bay" and that the fighting among these anti-ISIL forces "would slow the process to liberate the remaining territory from IS".

"The government of the Kurdistan-Iraq region has committed itself, by final declaration, to use the delivered weapons only for the fight against the so-called Islamic State and in accordance with international humanitarian law", a defence ministry spokesman told Der Spiegel on 6 March.