The Montreux Convention Regarding The Regime Of The Straits: A Turkish Perspective

The Montreux Convention regarding the regime of the Turkish Straits was signed on 20 July 1936 in Montreux. With this convention, the Republic of Turkey managed to end the issue of Straits, which was resolved temporarily with the Treaty of Lausanne, so as to protect its own safety and interests.

Considering the historical developments, Turkey had to allow the Straits as a gun-free zone to be administered by the Straits Commission under the Treaty of Lausanne. This situation which threatened Turkey’s absolute sovereignty and security over its territory had to be corrected due to the increasing political tensions in Europe in the late 1930s. The Montreux Convention was the result of the political and diplomatic efforts that were made in this direction.

Through this convention that was signed by Australia, Bulgaria, Great Britain, Japan, France, Romania, the Soviet Union, Yugoslavia, Greece and Turkey, Turkey’s limited rights were given back. Turkey gained sovereignty over the Straits Zone. The USA was also invited to the conference that was held before the convention. However, the Washington Government preferred not to participate and thus couldn’t become a signatory.


Northwestern Turkey is divided by a complex waterway that connects the Black Sea to the Sea of Marmara and the Aegean Sea. The channel passing between the Black Sea and the Sea of Marmara is named the İstanbul Boğazı, more commonly called the Bosporus. Istanbul, the largest city of Turkey is positioned at the south end of the Bosporus. The Sea of Marmara is connected to the Aegean Sea by a channel called the Çanakkale Boğazı, also known as the Dardanelles. The Turkish Straits, comprising the Strait of Canakkale, the Strait of Istanbul and the Sea of Marmara, are unique in many respects. The very narrow and winding shape of the strait is more akin to that of the river. It is an established fact that the Turkish Straits are one of the most hazardous, crowded, difficult and potentially dangerous waterways in the world for marines. All the dangers and obstacles characteristic of narrow waterways are present and acute in this critical sea lane.

The Montreux Convention guarantees free passage of civilian merchant ships without any restriction through the Dardanelles, the Sea of Marmara and the Bosporus in peacetime. Therefore, the adoption of the Turkish Straits Vessel Traffic Services System, which was put into practice by Turkey when the number and tonnages of vessels passing through the straits increased dramatically, became possible after serious diplomatic negotiations between the signatories of the Montreux Convention.

Six out of 29 articles of the Montreux Convention were related to the civilian merchant ships while 16 of them were related to warships and aircraft. Provisions regarding the passing of warships through the Straits vary depending on whether these ships belong to a country with or without a shore on the Black Sea. Also, these provisions vary depending on whether Turkey is belligerent or sees itself under a close war threat.

The definition of “ton” in the Montreux Convention, unless otherwise specified, refers to the long ton, which is equal to 1016 kg (2240 pounds) instead of the metric ton that is equal to 1000 kg.

Passage of warships
The Black Sea riparian countries have the right to transit their warships and submarines through the Straits without any tonnage restriction provided that Turkey is notified eight days prior to the transit passage through diplomatic channels

Ships that have a greater tonnage than 15.000 tons may pass through the Straits one by one and be escorted by not more than two destroyers.

Only submarines belonging to riparian states can pass on the surface and singly through the Turkish Straits, for the purpose of rejoining their base in the Black Sea for the first time after their construction or purchase, or for the purpose of repair in dockyards outside the Black Sea.

There are severe restrictions in terms of type, number and tonnage for the transit through the Straits of warships that belong to the non-Black Sea countries. These non-riparian countries are required to notify Turkey 15 days, prior to the transit through diplomatic channels.

The total number and the maximum aggregate tonnage of all foreign naval forces which may be in course of passage through the Turkish Straits are limited to 9 and 15.000 tons respectively. The maximum aggregate tonnage that non-riparian States may have in the Black Sea is 45.000 tons. In this regard, the maximum aggregate tonnage of the vessels of war that one non-riparian State may have in the Black Sea is 30.000 tons. The non-riparian states cannot keep their warships for more than 21 days in the Black Sea.

Due to its date of signing, the Montreux Convention does not have a clear statement with regard to nuclear-powered vessels. In fact, in the convention, there is not a statement with regard to the engine types of the ships that will pass through the Straits. In theory, the transit of a nuclear-powered ship through the Straits is not restricted. However, today nuclear-powered warships are either submarines or aircraft carriers with huge tonnage.

The transit of a submarine or an aircraft carrier belonging to a country without a shore on the Black Sea is not possible. Therefore, a nuclear-powered warship has not passed through the Straits officially so far.

The only type of warship that is exclusively banned from passage through the Turkish Straits is the aircraft carrier.

Turkish Straits during a War or Crisis
In the time of war Turkey not being belligerent, the peacetime rules apply for the warships belonging to non-belligerent parties. Warships belonging to the waring states cannot pass through the Turkish Straits, The only exception of this is that if the warships belonging to belligerent countries with or without a shore on the Black Sea have already left the ports that they are affiliated to before the war, they have the right to transit in order to return to their ports.

In time of war, Turkey being belligerent, the passage of warships is entirely left to the discretion of the Turkish Government.

The Southern enterance of the Bosphorus. The old city, The Golden Horn are visible at the bottom. At far left the first Bosphorus Bridge can be seen.

Similarly, if Turkey considers itself to be threatened with imminent danger of war, the transit of warships belonging to foreign countries through the Straits is left to the discretion of the Turkish Government.

By means of this authority, Turkey can prohibit the transit of warships belonging to the countries that cause Turkey to consider itself to be threatened with the danger of war while it can allow the transit of warships belonging to countries that do not cause that such situation.

With the Montreux Convention regarding the regime of the straits, which we have tried to summarize above, the number, type and size of the warships that can reach the Black Sea have been restricted. These restrictions increased the security of the riparian states. However, the same restrictions prevent the desire of countries with powerful naval forces to be present and cruise in all seas all around the world.

Turkey has been trying to implement the Montreux Convention with great precision since 1936. Therefore, occasionally Turkey is exposed to criticism from countries both with and without a shore on the Black Sea. The first big test of the Montreux Convention was, no doubt, the Second World War. Turkey closed the Straits to the warships of the belligerent countries during this war in which Turkey remained neutral. This situation served the purpose of the Soviet Union since the transit of German submarines and warships through the Straits was prevented. Axis countries couldn’t bring new warships to the Black Sea except for those that were already in the Black Sea before the war. Submarines were transferred in pieces by land or through the Danube River so that they could be assembled in Romania.

This however also prevented the military aid convoys coming from its allies, the UK and the USA, to pass through the Straits. Therefore, much of the military aid from the USA and UK had to be carried to Russia either over Iran or over the North Pole route.

Montreux During The Cold War
During the Cold War, Turkey was exposed to criticism both from the Soviet Union and the NATO allies from time to time due to its way of implementation of the Montreux Convention.

In 1976 when Turkey allowed the warship Kiev to pass through the Turkish Straits, many NATO allies including the USA protested Turkey. The Kiev, constructed in the Nikolayev Shipyard in the Black Sea in 1972 was considered as the first aircraft carrier constructed in the Soviet Union. However, having been quite aware of the fact that violating the Montreux Convention would not be good for its own benefit, the USSR classified Kiev as a heavy anti-submarine cruiser.

The Montreux Convention, defines aircraft carriers as surface warships, regardless of their tonnage, designed and constructed mainly to carry aircraft and enable their operation of them. If a warship was not designed or constructed with the sole purpose of carrying and operating aircraft, is not considered as an aircraft carrier even if the ship has a suitable deck for the aircraft’s take-off and landing.

Kiev and her sister ships had long-range anti-ship and air defence missiles as well as anti-submarine warfare rockets. Thus, the Soviet Union was able to classify these ships as heavy anti-submarine cruisers. All the ships of this class, Kiev, Minsk, Novorossiysk and Baku passed frequently both northbound and southbound through the Turkish Straits while they were commissioned.

This is not a carrier. Admiral Flota Sovetskogo Soyuza Kuznetsov passing through Bosphorus

A similar crisis happened in 1991 when Admiral Flota Sovetskogo Soyuza Kuznetsov, still commissioned in the Russian Naval Forces, passed through the Turkish Straits. Although this ship looked like a classical aircraft carrier in terms of its structure, the Soviet Union classified it as a heavy cruiser due to weapon systems deployed onboard. Again some NATO members put serious pressure on Turkey not to allow this ship to pass through the Straits, but they didn’t succeed in this effort.

Unlike Kiev class ships, the Admiral Flota Sovetskogo Soyuza Kuznetsov didn’t pass through the Straits ever, after leaving the Black Sea in December 1991.

Montreux in the New World
After the terrorist attacks on 11 September 2001, the U.S. Government requested help from the NATO countries within the scope of Article 5 of the NATO Treaty. According to this article, an armed attack against a NATO country is considered an attack against all of the NATO countries.

In this context, on 26 October 2001 Operation Active Endeavour (OAE) the first anti-terror operation of NATO was launched. The operation began with the patrols of the warships belonging to NATO countries in the Eastern Mediterranean was later on expanded so as to search the suspicious ships and their loads.

Upon the success of the OAE in the Eastern Mediterranean, the operation was expanded to the whole Mediterranean in March 2004. At the same time, the Turkish Naval Forces launched Operation Black Sea Harmony (OBSH). The purpose of OBSH was to ensure security in the Black Sea, create situational awareness and control suspicious merchant ships. The recognized maritime picture obtained within the scope of the operation, which is still ongoing, is shared with the NATO authorities and headquarters.

Initially, only units of the Turkish Naval Forces participated in OBSH. Later Turkey invited all littoral countries in the Black Sea to participate in the operation that was launched with its own initiative, and Romania, Russia and Ukraine responded positively to this invitation. The most important effect of the OBSH was that all the pressure exerted to modify the Montreux Convention and expand the OAE into the Black Sea was neutralised. Otherwise, if OAE was extended into the Black Sea, warships belonging to non-riparian NATO countries would be regularly present in the Black Sea and successful implementation of the Montreux Convention would be jeopardised.

After the Russian invasion of Georgia in 2008, the Montreux Convention was widely discussed again. Turkey received a lot of flak for refusing the transit of the hospital ship USNS Comfort. The USA wanted to dispatch the ship with a 69.552 displacement to Georgia to show solidarity and provide aid. However the article of the Montreux Convention is very clear about the sizes of the ships to be sent for humanitarian reasons: “In the event that one or more countries without a shore on the Black Sea desire to send naval forces into the Black Sea, for a humanitarian purpose, the said forces cannot exceed 8.000 tons.” The neo-conservative U.S. government was not happy with this decision.

The Russian annexation of Crimea in 2014, and NATO’s anti-ballistic missile defence system were the most recent times when Ankara faced pressure on how it implemented the Montreux Convention in dealing with foreign navies’ requests for transit to and from the BlackSea.

What Now?
Turkey will face challenges regarding the implementation of the Montreux Convention, especially after Ukraine calls on Turkey to close its airspace and the Black Sea access to Russian vessels on 24 February 2022. The Russian invasion of Ukraine showed that Russia indeed is the major challenge in terms of the security and stability of Europe in general and the Black Sea region specifically.

Turkey created a security architecture in the Black Sea with the riparian states. This apparatus keep the security in the region and keep the warships of the non-riparian states out. This architecture worked when the Russian Black Sea Fleet was weak and the NATO’s enlargement toward the east was slow. It even survived the Russian attack on Georgia in 2008. However, in 2014, Russia’s annexation of Crimea meant the collapse of the regional security architecture.

In recent years, Russia displayed its discontent towards the existence of foreign warships in the Black Sea by shadowing them constantly and flying military planes aggressively low and close to these vessels of war. On the other hand, NATO is trying to find ways to keep more warships of non-riparian States in the Black Sea and keep them longer.

When determining ways to bring stability to the Black Sea region and to answer the security challenges caused by Russian aggression it is important to remember that the Montreux Convention is simply far more than just a treaty that regulates the passage of commercial and naval ships through the Turkish Straits.

The Montreux Convention completes the Treaty of Lausanne, allowing Turkey to have full and absolute sovereignty and security over its territory. Therefore it is vital for Turkey to keep the convention alive and relevant.

Note: I have first written this text in 2014 for the Turkish online defence magazine C4 Defence in Turkish. It was published in the March 2014 Issue. Since then it was also published on web site Second Line of Defense. I have changed the original text in light of the recent Russian attack on Ukraine.

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