The 1936 Montreux convention is an agreement concerning the regime of the Black Sea and the connecting straits. In response to Turkey’s request to refortify the area, the signatories to the Treaty of Lausanne and others met in Montreux, Switzerland and agreed to return the zone to Turkish military control. The convention allowed Turkey to close the straits to all warships when it was at war and to permit merchant ships free passage.

The opening sentence of the convention reads, “Desiring to regulate transit and navigation in the Straits of the Dardanelles, the Sea of Marmara and the Bosphorus comprised under the general term Straits in such a manner as to safeguard, within the framework of Turkish security and of the security of the Black Sea, of the riparan states, the principle enshrined in Article 23 of the Treaty of Peace signed at Lausanne on the 24th July, 1923”. Turkey is the custodian of the Montreux convention. The convention authorises Turkey to act as a sentinel of maritime passages on the Black Sea and connecting straits. The terms of the Montreux convention were largely a reflection of the international situation in the mid-1930s. The United Nations Convention on the Law of Sea (UNCLOS) that entered into force in November 1994 had prompted calls for the Montreux convention to be revised and adapted to make it compatible with the UNCLOS regime governing straits used for international navigation. It was decided that the Montreux convention would continue to govern passage in the straits given its status as a “long standing international convention” under Article 35(c) of UNCLOS.

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While it was designed for a particular geopolitical context and remains unchanged since its inception, the Montreux convention has endured as a solid example of a rules-based international order and most of its terms are still followed. The Montreux convention is 88 years old and stands as an international maritime law of prime importance as a part of UNCLOS, governing navigation on Black Sea and connecting straits. The Black Sea is an inland sea bordered by Ukraine, Russia, Georgia, Turkey, Bulgaria and Romania of which Bulgaria and Romania are EU members. These two countries along with Turkey are also members of NATO. The Black Sea is connected with the Aegean Sea through the Bosphorus, the Sea of Marmara and the Dardanelles and with the Sea of Azov by Kerch Strait. It is supplied by major rivers, principally, the Danube, Dnieper and Dniester. Consequently, while six countries have a coastline on the sea, its drainage basin includes parts of 24 countries in Europe. The Crimean Peninsula extends into it from the north.

The Black Sea hosts confluent and strategic trade routes among Europe, Eurasia, the Middle East and North Africa. Warm water ports are valuable to Russia as they are navigable round the year unlike many ports in northern Russia. During the Cold War, the former USSR became the dominant power in the region. It controlled the northern and eastern shores of the sea, with docile socialist Romania and Bulgaria in the west who were members of the USSR dominated Eastern bloc. Only NATO member Turkey served as a counterbalance to the Soviet Union in the Black Sea. It was for this reason that Black Sea was often referred to at that time as a Soviet lake. The geo-political advantage of Moscow in the Black Sea region changed after the end of the Cold War and dissolution of the USSR.

Russia experienced a reversal of fortunes in the region as Bulgaria and Romania joined NATO. Georgia and Ukraine also declared their intent to join the alliance carrying the risk of shifting the regional balance in NATO’s favour. Russia retained control over the bulk of the erstwhile Soviet Union’s Black Sea Fleet through a series of agreements with Ukraine that partitioned the fleet between the two countries and allowed Russia to lease the Ukrainian port of Sevastopol as the fleet’s base. Turkey had resisted the leasing of Ukrainian port as that would increase Russia’s domination in Black Sea.

Russia justified its war with Georgia in 2008 and with Ukraine in 2014 as necessary to prevent the strategic balance from shifting decisively in NATO’s favour should either country try to join the Western alliance and to scare other former Soviet states from aligning too closely with the West. Russia went into war with Georgia and Ukraine when NATO membership for these two countries was only a distant possibility. Russia now controls two-thirds of the Georgian coastline following the 2008 war.

Russia believes that threats from the Black Sea region have grown in recent years and are more than just regional hazards. The Black Sea’s proximity to the Russian heartland means that a considerable part of European Russia is within the range of NATO missile defence systems based in Romania. Russia sees this as an encroachment of Western strategic infrastructure in Russia’s neighbourhood and is intended to undermine Russian security. Russia has since used its 2014 annexation of Crimea and its subsequent build-up of naval, ground and air defence capabilities to remedy that weakness. Yet its aggressive reaction to Western naval and air patrols in and over the Black Sea clearly highlights continued Russian perceptions of vulnerability there.

The Black Sea is an important trade and transportation artery for Russia for export of oil and grain by ship. Moscow sees the Black Sea region as vital to its geo-economic strategy to project power and influence in the Mediterranean, protect its economic and trade links with key European markets and make southern Europe more dependent on Russian oil and gas. Russia also sees the Black Sea as an important security buffer zone, protecting it from the volatility that could emanate from the North and the South Caucasus, the mountain range between the Black and Caspian seas. But Russia has obvious disadvantages in the Black Sea due to combination of geography and politics that limits its access to the wider Mediterranean region. Although Crimea provides the Russian navy and tankers with access to warm water ports, all ships entering or leaving the Black Sea must pass through the Turkish-controlled straits of the Bosphorus and the Dardanelles, the two strategically important passageways between the Black and Mediterranean Seas.

Under the Montreux agreement, Turkey allows civilian ships to pass through the straits in peacetime and places some restrictions on military vessels not belonging to Black Sea littoral states. Turkey’s ability and unbridled authority to close the straits during a conflict has long been a major concern for Russia. Russia’s seizure of Crimea in 2014 had enabled it to deploy considerable additional naval capabilities in the region creating an aggressive and defencein-depth posture against other maritime forces in the Black Sea. Ukraine had lost the bulk of its navy after Russia’s annexation of Crimea. At the time of the 2022 Russian invasion, there were no NATO warships in the Black Sea other than those of NATO Black Sea member states. Just days after the start of Russian invasion of Ukraine, Turkey announced closure of the straits to all military vessels. There was a strong argument that in closing the straits to all warships except those returning to their home bases in the Black Sea, Turkey appeared to have exceeded the provisions of the Montreux convention. Only in situations where Turkey was a belligerent or considered itself threatened with imminent danger of war, did it have full discretion over the passage of warships through the straits.

The immediate reestablishment of NATO naval presence in the Black Sea on the pretext of providing reassurance to its Black Sea members (Rumania, Bulgaria and Turkey) could have made Russia retreat. Another shade of opinion from scholars and experts was that a blanket ban on warship transits was the most viable action and could also be credibly justified as preventing escalation. Turkey’s decision to close the straits severely handicapped Russia’s ability both to reinforce its Black Sea fleet and to support its naval presence in the Mediterranean. The Russian base at Sevastopol had forced its navy into a significantly more defensive posture at sea. Whether during the Ukraine war Turkey as the custodian and sole authority had correctly applied the Montreux convention is a question still under debate. The outlook in the Black Sea region does not favour Russia.

A scholarly report from Carnegie Endowment for International Peace states, “Europe’s push toward a zero-carbon target by 2050 and an increasingly competitive gas market for both liquefied natural gas and Azerbaijani pipeline gas will undercut Russia’s economic leverage. Moscow may have stopped Georgia and Ukraine from joining NATO but in doing so, it has turned both countries into permanent enemies, whose presence on the Russian border and growing ties with NATO will require Russia to maintain significant military assets. Russian aggression in the Black Sea region has also caused other former Eurasian states to question Russia’s reliability and intentions, reinvigorating these states’ efforts toward multi-vector diplomatic and security strategies.” Russia’s attempts to dominate the Black Sea have inadvertently encouraged the region’s gradual integration into the western political and security ecosystem.

The Black Sea is no longer a Soviet Lake. The Sea has become a geo-strategic turbulence for Russia. With depleting naval presence, Russia’s power and influence in the Black Sea faces the prospect of decline. For Russia, Black Sea is a stepping stone into other regions, specially Western Balkans and Eastern Mediterranean. Russia is finding it difficult to reinforce its Black Sea fleet due to Turkey’s strict adherence to the Montreux convention. But that does not preclude Russia’s existing fleet from firing sea-launched cruise missiles against Ukrainian targets ashore. It has been reported that at the recently held NATO’s 75th anniversary at Brussels, the 32- nation alliance has discussed a plan to provide more predictable longer-term military support to Ukraine.

(The writer is a former central civil service officer who retired from the Ministry of Defence)