The Kerch Strait

What it is

The Kerch Strait connects the Black Sea to the Sea of Azov, lying between Russia's Taman Peninsula to the east and the Crimean Peninsula to the west. The channel is 4 to 15 kilometers wide and approximately 41 kilometers long, with a maximum depth of roughly 18 meters. It is the Sea of Azov's only maritime outlet, controlling access to Ukraine's ports of Mariupol and Berdyansk and Russia's ports of Azov and Temryuk. Before 2022, Mariupol's steelworks exported finished steel and pig iron through the strait; Berdyansk shipped grain and sunflower products.

The Crimean Bridge, spanning 19 kilometers across the strait, opened its road section in May 2018 and its rail section in December 2019. The bridge's main navigation span clears only 33 meters, restricting passage to smaller vessel classes and barring most Post-Panamax bulk carriers.

History

Greek settlers founded the colony of Panticapaeum on the Crimean shore in the 7th century BC. Ottoman forces held the strait for centuries until Russia acquired Kerch and the eastern approach under the 1774 Treaty of Küçük Kaynarca, then consolidated full control with the annexation of Crimea in 1783. Soviet forces built a rail bridge across the strait in 1944-1945; ice floes destroyed it in February 1945 and it was never rebuilt.

After the Soviet Union's dissolution, Russia and Ukraine signed the Treaty on Cooperation in the Use of the Sea of Azov and the Kerch Strait on December 24, 2003. The treaty declared the waters "internal" to both states, guaranteed free navigation for each party's commercial and military vessels, and required bilateral agreement before third-country warships could enter. It made no reference to UNCLOS, contained no international arbitration mechanism, and did not demarcate national maritime sectors.

Current state

Russia's March 2014 annexation of Crimea placed the strait under unilateral Russian control. On November 25, 2018, Russian Federal Security Service (FSB) coast guard vessels fired on and seized three Ukrainian Navy ships (the gunboats Berdyansk and Nikopol, and the tugboat Yany Kapu) attempting routine transit to Mariupol. Twenty-four sailors were captured. The International Tribunal for the Law of the Sea issued a provisional measures order on May 25, 2019 (Case No. 26, 19-1 vote) requiring Russia to release the vessels and crew; Russia did not comply, and the sailors were returned only through a September 2019 prisoner exchange.

Ukraine began targeting the Crimean Bridge after Russia's full-scale invasion in February 2022: a truck bomb damaged the road span on October 8, 2022; Ukrainian naval drones struck it again on July 17, 2023; and Ukraine's Security Service detonated roughly 1,100 kg of explosives at the bridge's underwater supports on June 3, 2025, closing it for several hours without causing structural collapse. As of mid-2026, Russia controls the strait entirely. The Permanent Court of Arbitration issued its award in Case No. 149 on April 22, 2026, finding Russia violated UNCLOS obligations related to the Crimean Bridge's environmental assessment but awarding Ukraine no compensation.

Relationships

The Turkish Straits (the Bosphorus and Dardanelles) are the Kerch Strait's direct upstream chokepoint: every vessel moving between the Black Sea and the wider ocean must transit Turkey's Montreux-governed passages. Together the two chokepoints define the Black Sea's maritime isolation. The fuel supply pressures in Russian-held Crimea have repeatedly exposed the peninsula's total logistical dependence on the Crimean Bridge, which is both the strait's fixed crossing and the only non-ferry link between Crimea and mainland Russia.

What to watch

Any Russia-Ukraine peace settlement will need to address whether Crimea's legal status reverts, whether the outstanding PCA arbitral findings bind both parties, and whether the Crimean Bridge's 33-meter clearance restriction poses an ongoing commercial liability. Cumulative structural damage from repeated Ukrainian strikes leaves the bridge's long-term freight capacity uncertain; a future catastrophic failure would force all Crimean logistics back onto Black Sea ferries, severing Russia's sole fixed rail link to the peninsula. The continued military campaign around Crimea makes near-term resolution unlikely. Russia's insistence on treating the Sea of Azov as bilateral internal waters, incompatible with Ukraine's UNCLOS-based claims, remains the unresolved legal fault line.