CHATHAM HOUSE - From parallel ambitions to colliding spheres: Iran–Turkey rivalry in a connected region - 7 July 2025 Hamidreza Azizi

 CHATHAM  HOUSE

From parallel ambitions to colliding spheres: Iran–Turkey rivalry in a connected region

7 July 2025

Hamidreza Azizi

Visiting Fellow, Africa and Middle East Division, at the German Institute for International and Security Affairs (SWP)

This article was written prior to the 12 June 2025 escalation between Iran and Israel.

The collapse of Syria’s Assad regime in late 2024 marked a turning point in Iranian–Turkish competition. It not only undercut Iran’s axis of resistance but also gave Turkey a decisive advantage in Syria and reinforced its hand in the South Caucasus as well. This shift has raised Iran’s threat perception across both regions, particularly as Ankara’s strengthened position could embolden it to advance the long-contested Zangezur Corridor as part of a broader project linking Central Asia to the Mediterranean. Tehran views this as strategic encirclement – one that would sever its land access to Armenia and marginalize its role in regional transit. Azerbaijan’s emerging role as a mediator between Turkey and Israel in Syria – and its broader coordination with both – has heightened Iran’s fears of encirclement and deepened its regional threat perception.

These developments illustrate a broader structural transformation in Iran–Turkey relations. Where competition once unfolded in relatively distinct spheres – Iran as the dominant force in the Levant and Iraq, and Turkey as a close strategic partner of Azerbaijan – it has now converged into a single geopolitical arena. As such, the rivalry is no longer parallel but fully interlinked, driven by overlapping ambitions, competing connectivity projects, and shifting alliances. As mutual threat perceptions deepen, the room for crisis management narrows, raising the risk of more volatile confrontations across an increasingly entangled regional landscape.

A shifting balance in the Middle East

Assad’s fall dealt a serious blow to Iran’s regional posture. Syria, Tehran’s principal state ally in the Arab world, was also a strategic conduit for its influence across the Levant. The regime’s collapse, combined with Hezbollah’s military and political weakening both regionally and within Lebanon following its latest war with Israel, has sharply curtailed Iran’s capacity to project power westward.

Meanwhile, Turkey has emerged as one of the primary beneficiaries of Syria’s power transition. Its longstanding support for rebel and opposition factions in Idlib has evolved into a strategic alignment with the new authorities in Damascus. Ankara now wields influence through its control of northern Syrian territories, deepening economic integration, growing political leverage in Damascus, and recent moves to secure a direct military presence. While it remains cautious of potential divergences with the new Syrian leaders, Turkey’s current military and diplomatic engagements reflect a significant strategic advantage in shaping Syria’s post-Assad order.

In Iraq, the Iran–Turkey rivalry has intensified. Numerous Turkish bases have been established in northern Iraq. Turkey says the bases are to counter the Kurdistan Workers’ Party (PKK).

This has led to friction with Iran-backed Popular Mobilization Forces (PMF), which view Turkey’s actions as infringements on Iraqi sovereignty. While Iran maintains significant influence in Baghdad and southern Iraq through Shia militias and political allies, Turkey’s growing ties with the Kurdistan Democratic Party (KDP) and economic engagements with both Erbil and Baghdad present challenges to Tehran’s traditional dominance.

The evolving Kurdish landscape could also reshape the dynamic between the two powers. Historically, Turkey viewed the PKK and its affiliates as security threats, prompting military operations in both Syria and Iraq. Iran, while officially designating the PKK a terrorist organization, pursued a pragmatic approach, balancing containment of Kurdish separatism within its borders with engagement with PKK-affiliated factions abroad – partly to offset Turkey’s influence. However, Ankara’s recent adoption of a more accommodating posture – marked by PKK leader Abdullah Öcalan’s February 2025 call for the group’s disbandment and the PKK’s subsequent decision to dissolve itself – could reinforce Ankara’s position. Iran’s ability to instrumentalize Kurdish groups is one of the few levers it has remaining to counterbalance Turkey’s regional influence. Should Turkey succeed in co-opting parts of the Kurdish political space, Tehran’s capacity to shape Kurdish dynamics in Iraq and Syria would diminish. Even more concerning for Tehran, PKK-aligned Iranian-Kurdish fighters may redirect their focus towards Iran, especially as the Kurdistan Free Life Party (PJAK) – the PKK’s Iranian offshoot – has rejected disarmament and remains active. In this context, Ankara’s leverage could potentially increase, turning a former Iranian asset into a liability.

Similar shifts may also play out in Syria. Iran has sought to exploit the looming US withdrawal and tensions between Syrian Kurds and the new government in Damascus. By doing so Tehran hopes to re-establish a foothold in the country. But evolving Turkey–Kurdish dynamics risk narrowing its ability to do so. In this context, Iran’s comparative influence across its traditional fronts in the Middle East – from Syria to Iraq – is increasingly constrained vis-à-vis Turkey.

Iran’s predicament in the South Caucasus

Turkey’s growing influence in post-Assad Syria has begun to reverberate beyond the Middle East, with implications now visible in the South Caucasus. Ankara’s expanded presence in northern Iraq and Syria, and its growing political leverage in Damascus, has broadened its strategic reach from the eastern Mediterranean to the Caspian Sea. This shift reinforces Turkey’s longstanding ambition to position itself as a central hub for east–west transit. One of the key initiatives Ankara has promoted is the Zangezur Corridor, which would connect mainland Azerbaijan to the Nakhchivan exclave via Armenia’s Syunik province, linking directly to Turkey.

The corridor holds significance beyond transit. It is central to Ankara’s Middle Corridor initiative, a trade and infrastructure route that is intended to connect China and Central Asia with Europe. In the context of shifting global alignments and efforts to diversify away from Russian and Iranian routes, this corridor is increasingly viewed as a potential anchor point for China’s Belt and Road Initiative (BRI).

For Tehran, the implications are considerable. The fall of Assad has already disrupted a proposed Iranian BRI route that envisaged linking Iraq and Syria to the Mediterranean. The realization of the Zangezur Corridor would sever Iran’s direct land access to Armenia and exclude it from major regional connectivity projects. Strategically, it would consolidate a Turkey-led Turkic arc along Iran’s northern border with both Central Asia and the South Caucasus, heightening Tehran’s concerns of encirclement and further constraining its perceived strategic depth. This would also leave Iran increasingly reliant on Turkey and Azerbaijan for access to the South Caucasus and beyond.

This threat perception has prompted a shift in Tehran’s behaviour. Iran has conducted military drills near its border with Azerbaijan and deepened ties with Armenia, including efforts to establish a framework for defence cooperation and the opening of a consulate in Syunik. These actions are aimed at signalling deterrence and asserting red lines. Yet they also reflect Iran’s increasingly reactive posture amid shifting regional balances, with limited tools to block the corridor outright.

Azerbaijan’s growing role as a diplomatic broker between Iran’s rivals – particularly its active mediation between Turkey and Israel aimed at managing tensions in Syria – adds to Tehran’s unease. It reinforces long-standing Iranian concerns about strategic coordination between Turkey, Azerbaijan and Israel, especially as such ties become increasingly visible across the Middle East and South Caucasus. Azerbaijan’s deepening military and intelligence partnership with Israel amplifies Iranian fears of encirclement. That this coordination now extends into Syria – once a central pillar of Iran’s regional influence – adds symbolic and strategic significance. At the same time, Ankara’s deepening diplomatic and logistical partnership with Baku could incentivize Turkey to more actively support Azerbaijan’s ambitions, including potential escalatory moves around Zangezur, which would further pressure Tehran’s position.

Russia’s evolving posture adds another layer of complexity. Moscow, once the guarantor of a relatively stable order in the South Caucasus, has grown more accommodative of Turkish interests since its invasion of Ukraine. By 2022, it had already accepted Turkey’s deeper role in the region following the Armenia–Azerbaijan war. With Assad gone, Moscow looks to Ankara to help preserve its military footprint and political relevance in Syria. In these new circumstances, Iran finds itself increasingly sidelined in a region where it once relied on Russian dominance to counterbalance Turkish and Azerbaijani assertiveness. In this sense, the reverberations of Middle Eastern realignments are acutely felt by Tehran in the South Caucasus.

What lies ahead for Iran and Turkey?

The weakening of Iran’s regional influence and the expansion of Turkey’s footprint across both the Middle East and the South Caucasus have shifted the balance between the two, transforming a traditionally compartmentalized rivalry into a multilayered and interconnected contest. Turkey’s strategic leverage now rests on not only its military presence and diplomatic partnerships, but its assertive transit and corridor diplomacy.

These developments are viewed by Tehran as a geopolitical crisis with long-term implications for its national security and regional standing. In response, it has adopted a two-pronged strategy. The first involves escalating military preparedness, conducting border drills, and deepening ties with Armenia – measures intended to deter further Turkish–Azerbaijani assertiveness in the South Caucasus. The second, in recognition of its growing limitations, focuses on managing tensions through diplomatic outreach. President Masoud Pezeshkian’s recent visit to Baku and a new agreement with Ankara aimed at expanding bilateral trade to $30 billion reflect this parallel track of crisis management. However, it remains uncertain whether trade deals, security talks, or regional diplomacy can meaningfully offset Iran’s structural disadvantages.

The trajectory of US–Iran negotiations adds further uncertainty. Renewed talks mediated by Oman offer a potential off-ramp from external pressure for Tehran. If successful, they could reduce regional tensions and, by removing sanctions, create economic space that might strengthen Iran’s strategic posture vis-à-vis Turkey. However, failure – or escalation into open confrontation involving Israel or the US – would not only deepen Iran’s vulnerabilities but could also indirectly reinforce Turkey’s regional standing in the medium to long term, despite potential short-term security challenges for Turkey as Iran’s neighbour.

Amid this shifting landscape, Iran and Turkey are attempting to manage an increasingly precarious relationship through ad hoc diplomacy. But their geopolitical agendas remain in conflict. The growing entanglement of regional theatres and the multiplication of contested arenas increase the likelihood of future flashpoints, making this rivalry more volatile and harder to contain. Although a direct confrontation may not be imminent, the stakes are now considerably higher.

This article is part of a policy series for the ‘Evolving Turkey–Iran relations and implications for regional reordering’ project of the Centre for Applied Turkey Studies (CATS) network.  

The Centre for Applied Turkey Studies (CATS) at the Stiftung Wissenschaft und Politik (SWP) in Berlin is funded by Stiftung Mercator and the Federal Foreign Office. CATS is the curator of the CATS Network, an international network of think-tanks and research institutions working on Turkey.