Can Turkey close the Bosphorus and Dardanelles straits to Russian ships?

The Turkish Foreign Minister declared that, according to Ankara, the war in progress in Ukraine is to all intents and purposes a war: and this allows Turkey to act in accordance with the provisions of the Montreux Convention and block some Russian ships. But what exactly does it foresee? And what exceptions are there?

In an interview with CNN on February 27, Turkish Foreign Minister Cavusoglu stated that – according to Turkey – the Ukrainian conflict is properly a war for the purposes of Article 19 of the Montreux Convention on the regime of the Straits and that, therefore, Ankara will implement this Convention in a transparent manner.

What does this 1936 international treaty have, and what are its implications for the Ukraine crisis?

The Convention outlines the legal regime applicable to transit through the Straits of the Dardanelles and the Bosphorus.

These straits divide the European and Asian parts of Turkey and connect, via the Sea of ​​Marmara, the Mediterranean Sea with the Black Sea.

Before the adoption of the Montreux Convention, the Turkish Straits regime was governed by the 1923 Lausanne Peace Treaty, which sanctioned the principle of free transit and navigation for all civilian and military ships, both in times of peace and of war. .

Free transit through the straits is now recognized, in general terms, also by the United Nations Convention on the Law of the Sea of ​​1982. This, however, recognizes the possibility of derogations from the general principle in the case of international conventions in force for a long time.

The Montreux Convention certainly falls among these, and attributes to Turkey the power to restrict the transit of ships across the Bosphorus and the Dardanelles. The adoption of the Convention responded to the interest, on both the Turkish and Soviet sides, of prevent the Black Sea from becoming an area of ​​possible naval confrontationpreventing the gathering of ships belonging to hostile powers and thus protecting the security of the coastal states.

To this end, the Convention provides various provisions to regulate the passage of military and commercial naval traffic through the Turkish straits.

In its history, the Montreux Convention assumed particular importance on the occasion of military conflicts in the Black Sea area. In particular, during the Second World Warthrough the application of the Convention, it was regulated with much thought the passage of German ships aimed at supplying the troops engaged on the eastern front and, after 1944, the transit of Russian shipping towards the Mediterranean.

The Convention assumed particular relevance also during the Arab-Israeli war of 1973when the restrictions placed on the passage of Soviet ships in the Mediterranean contributed to reducing the tension with the American fleet present in the area.

With regard to military trafficking in peacetime, the Convention provides the obligation to notify the passage to the Turkish government at least eight days before the transitas well as an overall tonnage limit of 15,000 tons And a maximum of nine naval units.

These limits do not apply to states bordering the Black Sea, such as Russia, provided that the vessels concerned pass through the straits individually. precisely through this rule that during the last few weeks several Russian ships from the Baltic and Pacific fleets have freely entered the Black Sea.

In the event of war, things change.

Article 19 of the Convention provides that, when Turkey is not among the warring parties, the military ships belonging to the states involved in the conflict cannot pass through the straits.

The closure of the Turkish straits in these cases therefore an operation substantially required by the Convention itself. It should be added that over the years Turkey has committed itself to a rigorous application of the Convention, aware of its importance for security in the Black Sea.

The most relevant news, therefore, is not the closure of the straits, but the formal recognition by the Turkish side that the Ukrainian situation constitutes a war – a term always avoided by Russia – such as to require the implementation of the relevant provisions of the Montreux Convention.

Article 19 also provides for some exceptions to the prohibition of passage. In particular, it sanctions the right for ships belonging to warring states to transit peacefully across the straits to return to their naval bases.

This provision would still make it possible for Russian ships to pass through, as well as for any Ukrainian ships, to return to their Black Sea ports. For example, Russian ships Marshal Ustinov and Varyag would currently be cruising off the Syrian coast with their own ships. escorts, which were deployed by the Russian Navy to strengthen its presence in the Mediterranean. These units may be affected by the Article 19 exception.

In an interview with CNN, the Turkish Foreign Minister warned that this exception must not be abused, and that the ships that use it must not then be employed in war operations.

The scenarios would change significantly if it were invoked Article 21 of the Montreux Conventioninstead of Article 19.

Article 21 provides, in fact, that the authorization to pass through the straits left to the discretion of the Ankara government if Turkey considers itself threatened by an imminent war danger, although not directly involved as a belligerent state. Notwithstanding the provisions of the previously discussed provisions, in this case the Convention allows Turkey to prevent ships belonging to the country from which the threat comes from returning to their bases.

This scenario, with respect to which some exceptions could also be configured, could generate more complex situations to manage.

* Paolo Busco and Andrea Mensi are international lawyers, respectively at Twenty Essex Chambers of London and the University of Lugano of Switzerland.


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