Few outside forces that are not directly involved in the conflict in Iraq have more at stake in the outcome of the battle over Mosul than Gulf Arab countries. In particular, the war of words that has erupted between Turkish President Recep Tayyip Erdogan and Iraqi Prime Minister Haider al-Abadi over the Turkish role in Iraq touches on a number of their most central concerns. As the offensive to reclaim Mosul from the brutal rule of the Islamic State in Iraq and the Levant has finally begun, Turkey has unexpectedly insisted on playing a direct role in the campaign. Indeed, Ankara asserts that it has already contributed artillery to the fighting, although Iraqi leaders deny this. The sudden introduction of Turkish forces into the conflict, and Turkey’s increasingly assertive role in Iraq more generally, is undoubtedly viewed with a mix of reassurance and anxiety, and hence a degree of ambivalence, by the Gulf states. Ankara’s boldness regarding Mosul involves both positive and negative elements for the Gulf states’ interests, and presents them with a set of complex challenges and opportunities. But the primary effect of this disruptive sideshow to the effort to expel ISIL from Mosul will be to redouble the determination of Gulf states to play a significant role, albeit indirectly, in shaping the outcome and aftermath of the conflict.

Turkey’s intervention has been prompted by a number of vital concerns for Ankara. The most important of these is Turkish concern about the influence and behavior of Kurdish forces in the region, particularly as its decades-long conflict with the separatist Kurdistan Workers’ Party (PKK) has flared in recent months. The PKK and its allies took advantage of the chaos in Syria, and the withdrawal of Syrian government forces from some Kurdish areas in the north, to establish two autonomous Kurdish zones along Turkey’s southern border. In September, Turkish forces intervened in northern Syria ostensibly to drive ISIL forces out of Jarablus. But their real intention was to prevent PKK-aligned Kurdish forces from linking two sizable strips of Kurdish-controlled territory along the Turkish border and creating a large and contiguous Kurdish enclave, controlled by the PKK, along Turkey’s underbelly.

The PKK has also emerged as one of the most effective fighting forces against ISIL, and has, in effect, morphed into a key U.S. ally against ISIL fighters, stoking grave concern in Turkey. PKK forces played the key role in several major assaults against ISIL in northern Syria, and participated in a number of campaigns against ISIL in Iraq as well. In order to counter what it perceives to be a growing PKK threat, since 2014 Turkey has maintained 600 to 800 troops inside Iraq in Bashiqa, which is near Mosul, and has been training other Kurdish and Arab militia groups. Iraq has denounced the Turkish presence in its territory and has become increasingly outspoken about its illegitimacy.

The Turkish demand for a direct military role in the Mosul operation is intended to prevent the PKK and its key allies from being strengthened by their involvement in the campaign. One of the challenges for Turkey will be to maintain, and perhaps even strengthen, close ties to the quasi-autonomous Kurdistan Regional Government in Iraq. Turkey’s support for the KRG is, in part, designed to ensure that Kurdish national ambitions are played out in Iraq, and not in Turkey, and are led by Iraqi Kurdish parties rather than the PKK. But, like Turkey, the PKK has been active in northern Iraq, and the KRG has had to balance its close economic and political ties to Turkey with its ethnic and national sympathies with the PKK. Therefore, Turkey will seek to use its expanding role in Iraq to bolster ties with the KRG while keeping the PKK in check. The pitfall, of course, is that the KRG cannot be seen as effectively siding with Turkey against the PKK, meaning that if the situation is not handled deftly, Turkey’s expanding military presence in Iraq might eventually undermine its close relations with the KRG, thereby upsetting its delicately balanced policy toward Kurdish nationalism.

Turkey has also framed its role in Iraq as protecting the minority Turkoman population in the Bashiqa area, and defending Sunni sectarian interests more broadly. It is this goal that has made Turkey an important de facto ally for the Gulf states in their efforts to limit the spread of Iranian influence in the Arab world. Turkey’s manner of expressing its Sunni Muslim sectarian identity in the broader Middle East has often been at odds with some of the Gulf states, most notably Saudi Arabia and the United Arab Emirates. Erdogan and his ruling party have been closely aligned with Muslim Brotherhood groups in the Arab world, a position shared only by Qatar for most of the past decade. But because Turkey’s influence has been limited, and Muslim Brotherhood parties have largely failed to secure power in post-dictatorship Arab republics, this issue is no longer a major source of disagreement between Ankara and Riyadh, although the UAE remains implacably opposed to all forms of Islamism. Moreover, when it has come to regional conflicts that are primarily defined in broadly sectarian terms, such as the wars in Syria and Iraq, Turkey and the Gulf states have been natural allies in support of Sunni Muslim forces (with the obvious exception of Salafist-jihadist groups like al-Qaeda and ISIL).

The Gulf states therefore appear to be quietly and cautiously supportive of Turkey’s expanded role in northern Iraq, since they view Turkey as an important counterweight to Iranian influence in Iraq specifically and the Middle East more broadly. The concern, however, is that intervention by the Turkish military could lead to an expanded role for pro-Iranian Shia Iraqi militias operating under the umbrella name of the Popular Mobilization Units. The campaign to liberate Mosul is currently being spearheaded by 30,000 Western-trained Iraqi government, Kurdish, and Sunni tribal forces. There has been a tacit understanding among the key players, including the Iraqi government and Iran, that PMU forces would not enter Sunni population centers during the Mosul campaign. Previously, they were successfully held back during the liberation of Falluja, following widespread concern that they might try to take vengeance against the Sunni Arab population in that city.

Should Turkish forces enter the fighting in and around Mosul in a significant way, because they are seen as representing Sunni sectarian interests and, in particular, acting as a counterweight to offset Iran’s power, this could provoke the PMU and its Iranian sponsors to increase involvement in the conflict. Should PMU forces be deployed to counter an expanded Turkish role, two major negative consequences could ensue. First, many of these groups have a long history of brutality and human rights abuses against Iraqi Sunni civilians, and those could be repeated on either a small or large scale. Even the fear of such abuses would have a very negative impact. The second, and closely related, concern is that the direct engagement in Sunni population centers by sectarian Shia militias could greatly strengthen the hand of ISIL and produce such anxiety among vulnerable populations that it could receive a sudden wave of support driven by existential fear.

Therefore, while the Gulf states will welcome the Turkish role as a counterweight to Iran, they will share the concerns that it could also strengthen local, and possibly even regional, support for ISIL, if its fighters cast themselves as the only effective defenders of vulnerable Sunnis from brutal sectarian enemies. However, like most Arabs and many others, the Gulf states are leery of the neo-Ottoman rhetoric that Erdogan and his allies are promoting to rationalize their engagement in Iraq and their regional posture. Turkey is viewed as an important ally in several core goals: defeating ISIL, overthrowing Syrian President Bashar al-Assad, and countering Iranian influence.

But, especially given its imperial history, there is a latent anxiety that Ankara could once again attempt to act as a hegemonic power in the Arab Middle East. Turkey may be seen as a key Sunni ally against Shia Iran, but it is also potentially a long-term non-Arab threat to Arab interests and even independence. Some of Erdogan’s recent rhetoric has raised the specter of not only Turkish historical resentment about the loss of its imperial possessions throughout the Middle East and grievances against the West, but also hints at considering redrawing the map to restore some of Turkey’s former territories. “We did not voluntarily accept the borders of our country,” Erdogan recently complained, adding that critics of Turkey’s role in Syria, Bosnia, and Iraq failed to understand that “these geographies are each part of our soul.” On October 21, Erdogan went even further, declaring that, “Mosul was ours. Look at the history.” Abadi has countered that if Turkish forces try to enter the fray in Mosul, what will await that will not be a “picnic.”

BBC reported that, in a nationalist fervor prompted by post-coup paranoia and chauvinism, “The Turkish media has been awash with maps showing Turkey’s widening horizons,” reflecting “irredentist cartography and rhetoric.” Erdogan has not specifically laid claim to any former Ottoman territories in Iraq or Syria, but this rhetoric inevitably produces anxieties in Arab lands formerly dominated by Ottoman rule. Moreover, for the Gulf states that value regional stability above most other policy considerations, such irredentist rhetoric is alarming. And while they greatly mistrust Abadi, the extreme arrogance of some of Erdogan’s comments aimed at the Iraqi prime minister, including telling him on October 11 that “you are not at my level” and demanding that he “know” his “place,” will ultimately not sit well with his fellow Arabs in the Gulf, who will inevitably wonder what “level” Erdogan accords them.

For all these reasons, tensions over Mosul are likely to increase the sense in the Gulf states that they need to find a way to ensure that they play a significant role in shaping the nature and outcome of the battle against ISIL. The rise of extremism among Sunnis and Shias alike is a major threat to the Gulf states. The prospect that the Mosul campaign could, in effect, strengthen the role and stature of sectarian Shia militias in Iraq and, simultaneously, play into the hands of ISIL, bolstering it politically even as military blows rain down on its forces, is deeply alarming. Saudi Foreign Minister Adel al-Jubeir said on October 17, “We oppose any kind of involvement by the Shia militias. If they go into Mosul … I would expect the negative reaction will be tremendous and if there are mass killings, it could end up being a bonanza for violent extremists, and recruitment for Daesh [ISIL]. It could add fuel to the sectarian fires raging in the region.” On October 13 Turkish Foreign Minister Mevlut Cavusoglu met with Jubeir and attended a Gulf Cooperation Council meeting focusing on Mosul. At a joint press conference following their meeting both men condemned the role of Shia militias in the conflict. Following the foreign ministers’ meeting, the GCC issued a statement warning that the PMU’s actions in the Mosul area “could trigger ethnic conflicts and jeopardize the operation’s success.”

While the Gulf states are alarmed at the real hegemony of Iran, they also worry about the potential hegemony of a neo-Ottoman Turkey. The only way to protect the Gulf state’s interests in Iraq is for these countries to play as strong of a strategic, albeit indirect, role in the liberation and post-conflict stabilization of Mosul as possible. To that end, the UAE recently pledged $50 million to reconstruction efforts for the city, and Kuwait also has a long-standing commitment. Their goals must focus on defeating ISIL, ensuring that Shia rule is not imposed on liberated Sunni areas, and maintaining Iraq’s independence and territorial integrity. It’s a tall order, but the liberation of Mosul is an opportunity for the Gulf states – even operating at a distance – to use their political, financial, and diplomatic clout to ensure that Washington, Baghdad, and Ankara work together with them to guarantee that liberated Sunni Arab territories do not fall under the control of Iran or proxies. If the Gulf states and their partners cannot safeguard the basic rights and security of Sunnis in Iraq, ISIL and other extremists will make the case over the long run that only they can.