On one front, opposing sides have joined forces to fight the Islamic State (IS). The enormous differences among the de facto allies reflect how much each sees IS as an existential threat, and the importance they attribute to Iraq. While US warplanes carpet bomb positions of the group in Mosul and its surroundings, Iraqi security forces, Iran-backed Popular Mobilization Units and Iraqi Kurdish peshmerga all advance.

Iranian military commanders from the Islamic Revolutionary Guard Corps (IRGC), though outside the spotlight, lead the Popular Mobilization Units and are keen to achieve a victory that could be built upon in the broader regional strife. Yet, they aren’t the only Iranians on the Iraqi front. A group of Iranian Kurdish separatists opposed to the Iranian government is reported to be fighting alongside the Iraqi Kurdish peshmerga, the armed forces of the Kurdistan Regional Government (KRG), which is also an ally of Iran. The Iranian Kurdish group is made up of several movements, including the Kurdistan Freedom Party (PAK) and the Democratic Party of Iranian Kurdistan (KDPI).

“A special forces team from our peshmerga forces, tasked with clearing land mines and other explosives, has been deployed to the front line against IS outside Mosul,” said KDPI spokesman Loughman Ahmadi in an interview with Al-Monitor. In his telling, “It is a national duty to defend all parts of Kurdistan, and IS is currently posing a threat to [Iraqi] Kurdistan.” He added, “Our peshmerga forces have more than 70 years of military experience. We have not received any military training by anyone except our own instructors. We are not under any ‘umbrella.’ Our special forces are helping the peshmerga forces of the KRG.”

A Sept. 8 report by the Associated Press quoted Hussein Yazdanpanah, a commander of the military wing of the PAK, as saying that his group has received military training and support from the United States as part of the international program to back Kurds in the war against IS in Iraq. Yazdanpanah added that the fight against IS "was never an alternative to their struggle" against the Iranian government. The KDPI spokesman added in his interview with Al-Monitor, “Iran sees us as one of its main enemies and would take every opportunity presented to attack us. The IRGC's ground force commander stated previously that Iran will attack members of our party and our peshmerga forces wherever and in whatever country they can.”