Despite the ideological crust that covers Iran’s politics, it could be said that Iranian diplomacy enjoys an amount of pragmatism that allows it to cope with changes. This was the case when the United States invaded both Afghanistan and Iraq in 2001 and 2003, respectively, and the series of events that have taken place in the region since then. Even when it comes to existential battles such as the one in Syria, Iran made the decision to fight until the end while preserving a line of dialogue with other players, directly or through mediators.
This was what Barzani believed would occur in the aftermath of the referendum. Therefore, he felt confident that neither Turkey nor Iran would be able to take any dramatic action. Still, this doesn’t mean the two powers aren’t going to take action at all, especially since both countries regard the Kurdish move as a threat to their national security.
To Iran, the referendum will have dire consequences on the future of neighboring Iraq. Having a Kurdish state could prompt the Sunnis to call for a referendum of their own, thus Iraq would cease to exist and would be replaced with three shaky sectarian or ethnic states. Kurdistan is a step toward “Shiitestan” and “Sunnistan” in Iraq. The border is a main concern for Tehran, especially because some Iranian Kurdish separatist groups function in border regions and have resumed their fight against the IRGC.
Since 2016, several attacks have been launched by groups whose headquarters are located in Iraqi Kurdistan. Now that the Kurdish region is planning to continue moving toward independence, Iran is going to be very concerned that these groups’ activities might have an impact on the internal Iranian front.