The fall of the Assad regime in Syria marks the end of Iran’s long-feared “Shia crescent” and the rise of Turkey’s “full moon”, reshaping the geopolitical landscape from the Horn of Africa to the Levant and Afghanistan. Recep Tayyip Erdoğan’s backing of the Syrian rebels has elevated Ankara to the status of a regional powerhouse, one whose influence now encircles all the major players in the region.

Turkey played a pivotal role in the rebels’ surprising triumph. The operation unfolded with an extraordinary lack of the kind of violent destruction that has characterised Syrian campaigns over the past 13 years. Turkey provided intelligence, guidance and political cover.

In the early years of the Syrian conflict, dozens of nations offered sporadic support to opposition groups, but Turkey’s commitment to the rebels in the north-western enclave near its border was consistent. Through ceasefires and frozen frontlines brokered since 2019, Turkey ensured that the rebels had the stability to rearm and reorganise.

With Iran stretched thin and unable to provide resources and manpower due to Israeli strikes against Hezbollah and Iranian networks in Lebanon and Syria, the collapse of Assad’s regime became not only possible but inevitable. Meanwhile, Russia, preoccupied with its war in Ukraine, offered only limited support to Assad.

The effects of Turkey’s success will likely be felt in neighbouring Iraq. Turkey has long maintained a presence in the northern regions and has collaborated with Iraqi Kurds and targeted the Kurdistan Workers’ party (PKK). The rise of a Sunni-led government in Syria strengthens Turkey’s hand in Sunni-majority areas of Iraq that have been dominated by Iranian-backed Shia militias since the fall of Islamic State in 2019. This gradual erosion of Iran’s influence in Iraq is likely to mirror the changes taking shape in Syria.

Turkey’s ambitions extend far beyond Syria and Iraq, reaching across Africa, the Caucasus and central Asia. Four days after the rebel victory in Syria, Erdoğan successfully mediated a deal between Somalia and Ethiopia, two close Turkish allies, to de-escalate tensions over territorial disputes. Turkey’s deep involvement in Libya, including military support for the UN-recognised government, also secures its influence over the Mediterranean’s energy dynamics and positions it as a key power broker in north Africa.

Ankara’s role in Afghanistan has also grown in recent years, where it has cultivated ties with the Taliban since its return to power in 2021, east of Iran’s borders. Additionally, Turkey solidified its presence in Azerbaijan near Iran’s northern border by backing Baku militarily and diplomatically during the 2020 Nagorno-Karabakh war against Armenia, positioning itself as a key player in the Caucasus.

Turkey’s rise complicates regional power dynamics, particularly for Saudi Arabia and its allies. Unlike Iran, whose sectarian Shia identity made it a clear rival, Turkey’s Sunni credentials create a more subtle and pervasive challenge. Riyadh has long positioned itself as the leader of the Sunni Muslim world, countering Iran’s Shia influence, but Turkey’s ascendancy disrupts this narrative. Ankara’s Islamist-leaning policies resonate with a broad swath of Sunni Muslims and political Islamists, offering an alternative to the Gulf monarchies.

Also unlike Iran, which relied on proxies such as Hezbollah to maintain its influence, Turkey has achieved legitimacy through its direct backing of local Sunni forces and popular causes such as the Arab uprisings of 2011. This positions Turkey as a more pan-Sunni power, undermining Saudi Arabia’s claim to regional leadership. For Riyadh and the UAE, this new dynamic is reminiscent of the 2012 rise of a Turkish-backed Islamist government in Egypt under Mohamed Morsi, which prompted Gulf states to support the military coup that ousted it.

For more than two decades, Iran’s Shia crescent symbolised its ambition to dominate the Middle East. Stretching from Tehran to the Mediterranean, this corridor allowed Iran to project power through proxies such as Hezbollah and threaten adversaries such as Israel and Saudi Arabia. By 2019, it seemed Iran had solidified its hold over four Arab capitals – Baghdad, Damascus, Beirut and Sana’a – marking the height of its regional influence. However, this expansion came at the cost of strategic overextension, leaving Tehran vulnerable to an increasingly assertive or aggressive Turkey and Israel.

Today, that crescent is fracturing. The rebels’ victory in Syria, coupled with Turkey’s rising influence, has severed Iran’s land bridge to Lebanon, disrupting its supply lines and isolating its proxies. This decline is further reflected in Lebanon, where Hezbollah’s dominance is under growing strain from both domestic crises and Israel’s persistent military pressure. Iran’s loss is Turkey’s gain, as Damascus shifts from being an Iranian ally for nearly half a century to a Turkish ally.

Turkey’s rise is not merely a response to Iran’s decline. It reflects an assertive foreign policy predicated on urgent economic and security imperatives, such as the Kurdish threat in Syria and Iraq, and a fundamentally different approach to regional power. While Iran’s influence relied on sectarianism and hard power, Turkey’s strategy combines military intervention with diplomatic outreach and economic investment. This multifaceted approach allows it to operate across sectarian and ideological lines.

In the region, Turkey’s dominance is a source of deep worry. For Saudi Arabia, the UAE and Israel, the shift in Damascus is a gamechanger that could pit them against a regional rival. For western policymakers, views of Ankara’s growing assertiveness range from concerns over its Islamist ties to recognition of its centrality to Middle Eastern politics. This plays into Ankara’s hands, as it is a marked difference to Iran’s power projection that was unanimously challenged in the west and the region.

In the years to come, the region’s power struggles will no longer revolve around the shadow of Iran’s ambitions but around the scope of Turkey’s. For rivals and allies alike, the question will no longer be whether Turkey will dominate the region, but how.

• Hassan Hassan is the founder and editor-in-chief of New Lines magazine

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