This chapter explores the Black Sea’s strategic significance for Europe and how the ongoing Russia–Ukraine war has reshaped the region’s security and political landscape.

Unlike the Baltic Sea, where littoral states are largely aligned as EU and NATO members, the Black Sea littoral states present a mosaic of political systems, security alignments and strategic priorities. Bulgaria and Romania are both EU and NATO members; Türkiye is a NATO ally but follows an increasingly independent course with regional power aspirations; Ukraine, Moldova[1] and Georgia are EU candidates, although the last appears to be drifting away; and Russia represents both one of the region’s major military powers and its main instigator of insecurity. This fragmented context, driven by widely diverging strategic interests, complicates any future models for coordination and governance.

Multilateral platforms such as the EU’s Black Sea Synergy and the Organization of the Black Sea Economic Cooperation (BSEC) have created frameworks for cooperation on energy, transport, and the environment.[2] However, they have been far less effective in addressing security concerns, particularly in the wake of Russia’s 2022 invasion of Ukraine. The resulting instability discourages investment and raises questions about the long-term viability of ambitious infrastructure projects.

Ripple effects

The Russian war against Ukraine has had divergent impacts on the littoral states. Georgia’s trade statistics have increased sharply, driven by growing commercial and business ties with Russia, an inflow of skilled IT workers, and the facilitation of sanctions evasion.[3] These developments have likely contributed to the ruling elite’s political shift away from the EU-accession track. Moldova’s trade and economy, by contrast, are suffering. Romania’s river ports, however, have benefited from increased traffic, providing a safe alternative route for regional exports and trade. This growth has enabled the renovation and expansion of both river and seaport facilities. Bulgaria’s artillery factories have been operating in three shifts since the start of the large-scale invasion. The industry is now seeking investment to expand production in the coming years.

The EU has also invested in improving road and railway connectivity between Romania, Bulgaria and Moldova. These upgrades could further strengthen North-South connectivity, a longstanding weak link in NATO’s eastern flank defence.[4] Türkiye, meanwhile, has leveraged its strategic position with both Ukraine (through the Grain Deal in 2023 and defence industry cooperation) and Russia (through trade and gas transit via TurkStream to Europe).

Despite these varied national priorities and differing impacts, all Black Sea littoral states share a common strategic reliance on access to the Black Sea – both the backbone of their economic security and a source of vulnerability. As one example, for Georgia, its role as a key transit corridor for energy resources (Figure 2) from the Caspian to European markets is both a blessing and a curse. The country faces pressure from both Moscow and Beijing to reorient its strategic direction towards their interests.[5] At the same time, the development of the Georgian deep seaports of Poti and Anaklia remains a geopolitical priority for the EU.[6]

Bulgaria is similarly exposed: around 70% of its transport activity passes through Varna and Burgas, the country’s main seaports (Figure 3). Russia continues to conduct military activities in Bulgaria’s exclusive economic zone, under the guise of drills, despite Bulgaria’s NATO membership. Repeated Russian drone incursions into Romanian airspace, as well as attacks on Ukraine’s Danube Delta ports such as Ismail and Reni, raise concerns over unhindered access to the Delta, with implications for regional trade and connectivity.[7]

Black Sea yearning

The Black Sea region’s long history of rivalry between the Ottoman and Russian Empires adds further complexity to its dynamics. The territory of contemporary Ukraine historically served as the Ottomans’ strategic northern buffer against Moscow’s ambitions to reach the Bosphorus and Dardanelles Straits, with three centuries of Russo-Turkish wars and Ottoman incursions testifying to the enduring strategic importance of Ukraine’s southern coast in this struggle.[8]

Today, the competition persists: Ukrainian drone and missile attacks on Russia’s Black Sea fleet are shifting the power balance in Ankara’s and NATO’s favour, effectively aligning Turkish and Ukrainian interests in deterrence and maritime security. Moreover, Türkiye has played an active role in efforts to end the war by brokering prisoner exchanges and restricting Russia’s naval presence in the Black Sea through the continued closure of the Turkish Straits, while maintaining its own independent and influential role outside the EU framework. Although its support for Russia currently remains measured, any shift towards a genuinely pro-Russian stance could create serious divisions within the NATO alliance. Still, there is significant potential for enhanced cooperation between the EU, Türkiye, and Ukraine to strengthen defence ties and address hybrid threats. Such collaboration would be mutually beneficial, bolstering Black Sea stability and reinforcing the broader European security architecture.

Geostrategic holy grail

The Black Sea has re-emerged as an arena of major geostrategic significance for Europe, particularly after Russia’s invasion of Ukraine in 2022 and the Israel–Gaza war in 2023, which disrupted major East Asia-Europe trade routes through Russia and the Suez Canal.[10] This has boosted the prominence of the Trans-Caspian International Trade Route (TITR), or Middle Corridor, linking China and Europe via Central Asia, the Caucasus, and the Black Sea. Trade along the Middle Corridor has expanded rapidly since its 2017 establishment by shipping, port, and railway companies from Georgia, Azerbaijan and Kazakhstan, boosted by key infrastructure upgrades – the 2014 Trans-Kazakhstan railway and the 2017 modernization of the Baku–Tbilisi–Kars line.[11] The TITR offers a faster and more secure alternative for connecting China and Europe through Central Asia and the Caucasus, thereby avoiding reliance on Russian infrastructure.

The Middle Corridor also aligns with EU efforts to diversify energy supplies and reduce dependence on Russian gas. In 2022, the European Commission committed €2.3 billion to a subsea electricity cable that will connect Azerbaijan, Georgia and Romania. This project has been labelled one of the Global Gateway’s flagship initiatives, reflecting the EU’s broader strategy to enhance sustainable and secure infrastructure across its partner regions.[13] Once operational, it will deliver enough renewable energy to power up to one million European homes. After renewable energy from Azerbaijan and Georgia reaches Romania, it will be integrated into the European grid, supplying electricity to multiple EU member states. Romania, which already generates over 11,000 MW[14] of renewable energy, primarily from wind and hydropower, is set to play a central role in this emerging energy corridor.

Beyond renewables, Romania’s Neptun Deep project, one of the EU’s largest offshore natural gas reserves in the Black Sea,[15] has the potential to transform regional energy dependency. It holds sufficient reserves to meet Romania’s own energy needs, already 80% domestically covered,[16] while also enabling exports to neighbouring Moldova and Bulgaria, reducing their reliance on Russian supplies and TurkStream. Russia is likely to actively oppose this shift, resorting to all available instruments of hybrid warfare, ranging from false-flag operations to potential attacks on energy infrastructure.

Uncertainty about how to respond to these threats and how to protect Exclusive Economic Zones (EEZs), which might fall outside Article 5 guarantees,[17] has prompted the EU to assert itself as a security actor. Its 2025 EU strategy for a secure, prosperous and resilient Black Sea region[18] links security, connectivity, and prosperity, aiming to create a Maritime Security Hub, mainstream defence cooperation, and foster dual-use infrastructure in the region.