Armenia’s intention to withdraw from a Russia-led security alliance of ex-Soviet states appears on the surface to offer an opportunity for the European Union, Turkey and Iran to expand their influence and pursue their own interests in the region.

However, their ability to fill the gap left by Russia’s declining role is restricted, as Azerbaijan, having won a war with Armenia in 2023, is keen to play by its own rules. So the three contenders for influence face limitations on their efforts.

The EU has been trying to take some of the heat out of relations between Azerbaijan and Armenia, mediating talks between them and hoping to cement its credentials as a geopolitical actor. Turkey wants to maintain its influence in its near region, and Iran can be assumed to want mainly economic benefits to alleviate the effect of international sanctions.

Armenia finally gave notice in June of its intention to leave the Russian-led Collective Security Treaty Organization (CSTO), after freezing participation in February. Armenia did so partly because Russia had not supported it against military offensives in which Azerbaijan successfully reclaim the disputed territory of Nagorno-Karabakh. Other factors were the ineffectiveness of Russian peacekeepers after the ceasefire and fellow CSTO-member Belarus’s sale of arms to Azerbaijan, revealed in leaked documents in June.

Conversely, Azerbaijan has become more assertive and felt less restrained by external pressure since its capture of Nagorno-Karabakh, its winning of new natural gas agreements and its gaining the honour of hosting the UN climate change conference in November this year, Azerbaijan sees no reason to give concessions to anybody. As long as Azerbaijan charts a more independent and combative course, the wider region should be wary.

The EU has been the main prospect in Armenia’s attempts to balance its foreign policy against Russian influence. Armenia has negotiated a comprehensive economic partnership agreement with the EU despite also being a member of the Eurasian Economic Union, the Russia-led would-be analogue of the EU. Suspicious of Russian peacekeepers, Armenia even requested that the EU deploy a monitoring mission to the Armenia-Azerbaijan border.

However, Armenia’s rejection of Russia as the region’s security guarantor does not automatically boost the EU’s capacity to promote security in the region. The EU’s monitoring mission is a temporary and limited measure and has been consistently undermined by Russia, which accuses the EU of peddling an enlargement and democratic reform agenda.

The EU’s credibility as a mediator is also threatened by Azerbaijan’s aggressive attempts to undermine France by fomenting unrest in New Caledonia and questioning the status of Mayotte. These are responses to what Azerbaijan sees as biased support for Armenia.

The EU faces a delicate balancing act as it tries to support Armenia against an increasingly assertive Azerbaijan, yet the EU itself cannot push too hard against Azerbaijan for concessions to Armenia as European countries are keen to import Azerbaijani natural gas as they reduce their dependence on Russian supply.

Then there’s Turkey, which the EU needs to consider because its pipelines carry the natural gas from Azerbaijan to Europe. As Russian influence weakens, Turkey may prefer not to support the EU as a competitor to its own ability to affect affairs in the region.

Turkey’s role in the region appeared most clearly in its military support to Azerbaijan. In particular, Turkish drones contributed to the Azerbaijani army’s edge over Armenian forces and facilitated the capture of Nagorno-Karabakh. Military support is probably a declining advantage however, since Azerbaijan has achieved its immediate objective of full control of Nagorno-Karabakh.

So Turkey’s influence in the region now relies on the alignment of political and economic objectives between Azerbaijan and Turkey. As the former becomes more assertive, Turkey’s influence can’t be taken for granted.

Iran has the most reason to be concerned by a weakened Russia. Among the countries that could gain regional influence as Russia loses it, Iran is the weakest. It lacks the EU’s economic weight and Turkey’s historical influence. Yet Iran needs stability across its border in the Caucasus as it seeks to overcome international isolation and is reliant on whichever economic corridors are available.

Indeed, Iran could see itself being undermined. An emboldened Azerbaijan could exert greater influence in the northern Iranian region that’s also called Azerbaijan and is home to an ethnic Azeri population. While Azerbaijan has not yet expressed a credible threat against Iran, Tehran is understandably concerned by this possibility.

The EU, Turkey and Iran are each pursuing its own interests in the Caucasus amid Russia’s declining influence. Yet Azerbaijan’s ascendant trajectory puts severe limitations on their ability to influence it and Armenia. Of the three, Turkey looks the least constrained.