Robert C. Castel: The Old-New Struggle for the Black Sea

The so-called "Turkish Lake" is a theater of operations that is of critical importance to the belligerents and the entire region.

Photo by Anatolii Stepanov / AFP

The security architecture of the Black Sea is anchored in the Montreux Convention (1936), which gives Turkey exclusive control over the Bosporus and Dardanelles Straits. The tyranny of geography and the convention based upon it have placed Ankara in a unique position: it acts both as the NATO system’s gatekeeper and as a proponent of its own regional (and partially neo-Ottoman) strategy. Some even go as far as to call Turkey the bouncer of the Black Sea.

Once referred to as the “sick man of Europe,” Turkey has long been the “owner” of the so-called Turkish lake. By controlling the straits, it enjoys exceptional strategic freedom. At the onset of the 2022 war, Ankara closed the straits to foreign warships, limiting both Russian and NATO naval operations.

Adding to Turkey’s influence is the still-in-planning Istanbul Canal—a proposed artificial waterway running parallel to the Bosporus. A fierce debate is already underway about whether the Montreux Convention’s restrictions would apply to this man-made route.

Russia’s 2014 annexation of Crimea drastically altered the region’s maritime legal and strategic status. In redrawing the maritime boundaries, Moscow claimed much of Ukraine’s continental shelf and several small islands and key locations—such as Snake Island—significant both militarily and in terms of resource accessibility, as well as  jurisdictional control. Russia has retained Sevastopol as a naval base but has relocated much of its fleet eastward to reduce vulnerability to Ukrainian strikes. Despite sanctions, resource shortages, and combat losses, the Russian fleet still wields considerable power through submarines, missile-carrying ships, and air defense systems.

Nonetheless, the Kremlin’s goals remain unchanged: assert dominance, push back NATO, and partially blockade Ukraine’s maritime lifeline.

With its traditional navy destroyed, Ukraine has turned to asymmetric warfare, relying heavily on surface-level, remote-controlled attack systems—a modern version of the historical “mosquito fleet” tactic. These have significantly undermined Russian naval dominance and demonstrate that the nature of naval warfare is fundamentally changing in the region.

Meanwhile, Romania and Bulgaria have expanded their strategic roles, primarily through NATO integration. Although their naval capacities are limited, they’ve become key players in logistics and grain export infrastructure, and are also seeking to boost their influence during ceasefire negotiations.

In summary, the following can be said regarding the issue of military balance in the Black Sea. At the tactical level, the balance between offense and defense has tipped in favor of the former, while at the strategic level, it favors the latter. This is why Russian never attempted an amphibious landing at Odesa, despite the destruction of the Ukrainian navy early in the war. In the age of shore-based anti-access/area denial weapon systems, the gap between major and minor powers has dramatically narrowed. While the minor powers may not be able to extend their dominance over the entire Black Sea, they can effectively defend home coasts against the power projection attempts of the major players.

One of the most crucial dimensions of Black Sea geopolitical dynamics is energy. The exploration of undersea hydrocarbon fields—particularly Sakarya (Turkey) and Neptun Deep (Romania)—could reduce dependency and thus Russia’s energy leverage in the long term. However, pipelines like TurkStream and Blue Stream still allow Moscow to maintain its influence westward.

Control over energy infrastructure in the region is not just a supply issue, but also a sovereignty issue.

Equally important are the undersea data cables: BSFOCS/KAFOS, the Russia–Georgia cable, and planned projects like the Black Sea Digital Connectivity Project and the Turkey–Ukraine data cable. Russia’s dominance over communications infrastructure raises serious concerns about espionage and sabotage potential.

Finally, the geopolitical role of migration routes through the Black Sea must be noted. The main route runs westward through Turkey, Bulgaria, and Romania, facilitating migration from the Middle East, Africa, and South Asia. A less significant eastern route exists but is more localized. Unlike the Mediterranean or Aegean Seas, sea-based migration across the Black Sea is minimal.

In conclusion: the Black Sea is not merely a regional body of water. It is a complex strategic arena where global power interests, historical legacies, and modern security challenges all intersect.

The author is a security policy expert at the Center for Fundamental Rights and a senior contributor to our newspaper.