Chronicle of the Middle East and North Africa

Montreux Convention: Turkey’s Card in the Ukrainian Crisis

Montreux Convention:
Russian Navy’s diesel-electric submarine Rostov-on-Don sails through the Bosporus Strait on the way to the Black Sea past the city Istanbul as Galata tower is seen in the background on February 13, 2022. Ozan KOSE/ AFP


Russia‘s war on Ukraine has brought a critical issue back to the surface: the free passage of warships across seas, straits, and territorial waters.

The whole issue popped out when the Ukrainian ambassador to Turkey, Vasyl Bodnar, asked the Turkish government to close the Bosporus and Dardanelles straits and deny the Russian warships entry. Turkey reacted, saying that it could only do so if what is happening in Ukraine is called a war officially, which is already the case. In other words, Turkey’s perception of the Russian-Ukrainian scene as a war gave it full authority to close the two straits. Turkey wields this control under an international convention signed 86 years ago.

Montreux Convention 1936

After WWI, the Bosporus and the Dardanelles were the most complex issues debated between Turkey and Western countries. These two straits connect the Aegean (thus, the Mediterranean) and Marmara and the Black Seas during wars and their aftermath. They control maritime traffic, including the movement of warships and merchant ships.

After the Treaty of Sèvres in 1920, Bosporus and the Dardanelles were subject to international administration through the League of Nations. However, after the Treaty of Lausanne in 1923, Turkey partially restored its control over the two straits in its territorial waters. It was allowed only to regulate merchant ships’ transit during peacetime.

However, the Bosporus and the Dardanelles remained under international auspices through a commission appointed by the League of Nations. Turkey was prevented from installing military forces and weapons on both straits. In other words, Turkey’s control over the straits remained incomplete until the signing of the Montreux Convention on July 20, 1936, in Switzerland.

The convention was ratified by the League of Nations, with France, Bulgaria, Greece, Japan, Romania, Yugoslavia, Turkey, the United Kingdom and the USSR’s consent. It is still binding, cancelling all the clauses regarding the two straits in the Treaty of Lausanne.

The convention included 29 articles, four annexes, and a protocol. It returned complete control over the Bosporus and the Dardanelles to Turkey in return for internationally agreed articles regarding the passage of ships and the use of the straits. Most notably, the convention defined ships into merchant and military ships, two conditions of peace and war, and two forms of states; riparian states of the Black Sea (Ukraine, Russia, Georgia, Turkey, Bulgaria and Romania) and non-riparian states.

Merchant ships have complete freedom of passage through the straits in peace. In war, Turkey has the right to prevent the passage of merchant ships of its enemies if it is a warring party. In cases where there are two other warring states, Turkey is not entitled to deny passage to merchant ships of either of them, except for ships carrying military equipment.

Passage of warships is subject to several conditions in peace and war. In peace, freedom of transit is granted after notifying the Turkish state. That excludes aircraft carriers since the defined weight of warships allowed to cross means no aircraft carrier can cross. But the term “aircraft carrier” was not mentioned in the treaty. In war, a distinction is made whether Turkey is a party in that war.

Turkey can use the straits while respecting international maritime laws in the first case. In the second case, Turkey has the right to impose its measures on warships of the warring countries. In other words, it has the right to stop the transit of ships, except for ships that return to their ports if they belong to a riparian state.

Implementing the agreement is binding unless a new agreement is arranged that cancels the Montreux Convention, which has not happened despite several attempts to form a new agreement or amend the old one’s terms.

Montreux Convention Over History

Over History, the Soviet Union considered the terms of this convention a threat to its interests and demanded amending it, especially during Stalin’s era. But in fact, the Soviet Union was among the first to benefit from them in World War II. Back then, the two straits were closed to the Axis forces, preventing them from sending their warships to fight the Soviet Union on its long shores on the Black Sea.

After WWII, the Soviet Union insisted on pursuing equal rights to those given to Turkey in the convention. The Russians’ rage because they couldn’t force an amendment on the convention led to the so-called Turkish Straits Crisis of 1947, which was part of the Cold War.

The Straits Crisis was a Turkish-Soviet conflict caused by Turkey’s restriction of Soviet ships’ passage through the Bosporus and the Dardanelles under the Montreux Convention. This crisis is considered the main reason for the Turkish-American rapprochement, which led to Turkey’s admission into NATO in 1952. This rapprochement stopped all Soviet military manoeuvres around the straits. After that, the Soviets stopped demanding privileges in the two straits or an amendment to the Montreux Convention.

The convention also restricted the United States military access to the Black Sea. Nevertheless, the Soviet Union continued to accuse Turkey of being soft regarding US warships’ passage through the straits.

Turkey itself also had reservations about the convention. However, despite constant international attempts and calls, Turkey is the most insistent on implementing the convention terms and preventing its amendment.

The convention was part of the debate over the Greek island’s crisis, as Turkey demanded to prohibit the arming of those islands. Turkey believes that Greece’s sovereignty over these islands is linked to their disarmament under the 1923 Lausanne Treaty.

On the other hand, Greece considers that the Montreux Convention abolished the articles relating to the two straits in the Lausanne Treaty. Accordingly, Greece believes that it has the right to provide weapons in the areas near Bosporus and the Dardanelles, which doesn’t sit well with Turkey. The latter considers that the abolished part is related to ensuring Turkey’s security. According to the Turkish perspective, only Turkey has the right to deploy forces over the two straits.

Montreux Convention and Istanbul Canal

A group of retired Turkish naval officers issued a statement on April 4, 2021, accusing the Turkish government of threatening the Montreux Convention by moving forward with the Istanbul Canal project. This project aims to construct an artificial sea-level canal to connect the Black Sea with the Sea of ​​Marmara to form a parallel waterway to the Bosporus Strait.

According to the statement, the canal project may put the convention up for debate again due to digging a new waterway connecting the two seas. The officers considered that the convention holds a “critical role in Turkey’s fate and survival.”

The Turkish government rejected and criticised the statement, considering who issued it “enemies of the republic” and “putschists.” In the same context, the statement did not receive explicit support from the Turkish opposition, which considered it just a “viewpoint,” and its patrons could not be classified as “enemies.”

Montreux Convention Today

A few days ago, Turkey exercised one of its convention rights, closing the two straits to warships in the event of a war. Accordingly, Russian warships will not cross, and Russia won’t deploy them to serve its war in Ukraine. Of course, in the coming days, this matter may bring back the convention issue again and another episode of Russia’s objection to the convention, and maybe more.