The (Montreux) Convention regarding the Regime of the Straits, often known simply as the Montreux Convention, is an international agreement governing the Bosporus and Dardanelles straits in Turkey. Signed on 20 July 1936 at the Montreux Palace in Switzerland, it went into effect on 9 November 1936, addressing the long running Straits Question over who should control the strategically vital link between the Black and Mediterranean seas.
The Montreux Convention regulates maritime traffic through the Bosporus and Dardanelles straits in Turkey. It guarantees "complete freedom" of passage for all civilian vessels in times of peace. In peacetime, military vessels are limited in number, tonnage and weaponry, with specific provisions governing their mode of entry and duration of stay. If they want to pass through the Strait, warships must provide advance notification to the Turkish authorities, which, in turn, must inform the parties to the convention. In wartime, if Turkey is not involved in the conflict, warships of the nations at war may not pass through the Straits, except when returning to their base. When Turkey is at war, or feels threatened by a war, it may take any decision about the passage of warships as it sees fit.
While it was designed for a particular geopolitical context, and remains unchanged since its adoption, the Montreux Convention has endured as a "solid example of a rules-based international order", since most of its terms are still followed.
Background
The convention was one of a series of agreements in the 19th and 20th centuries that sought to address the long-running Straits Question of who should control the strategically vital link between the Black Sea and Mediterranean Sea. In 1923, the Treaty of Lausanne had demilitarised the Dardanelles and opened the Straits to unrestricted civilian and military traffic under the supervision of the International Straits Commission of the League of Nations.
By the late 1930s, the strategic situation in the Mediterranean had altered with the rise of Fascist Italy, which controlled the Greek-inhabited Dodecanese islands off the west coast of Turkey and had constructed fortifications on Rhodes, Leros and Kos. The Turks feared that Italy would seek to exploit access to the Straits to expand its power into Anatolia and the Black Sea region. There were also fears of Bulgarian rearmament. Although Turkey was not legally permitted to refortify the Straits, it nonetheless did so secretly.
In April 1935, the Turkish government dispatched a lengthy diplomatic note to the signatories of the Treaty of Lausanne proposing a conference to agree a new regime for the Straits and requested that the League of Nations authorise the reconstruction of the Dardanelles forts. In the note, Turkish Foreign Minister Tevfik Rüştü Aras explained that the international situation had changed greatly since 1923. Europe had then been moving towards disarmament and an international guarantee to defend the Straits. The Abyssinia Crisis of 1934–1935, the denunciation by Germany of the Treaty of Versailles and international moves towards rearmament meant that "the only guarantee intended to guard against the total insecurity of the Straits has just disappeared in its turn". Indeed, Aras said that "the Powers most closely concerned are proclaiming the existence of a threat of general conflagration". The key weaknesses of the present regime were that the machinery for collective guarantees were too slow and ineffective, and there was no contingency for a general threat of war and no provision for Turkey to defend itself. Turkey was therefore prepared to enter into negotiations with a view to concluding, in the near future, agreements for regulation of the Straits with essential security provisions for the inviolability of Turkey's territory, and also for continued development of commercial navigation between the Mediterranean and the Black Sea.
The response to the note was generally favourable; Australia, Bulgaria, France, Germany, Greece, Japan, Romania, the Soviet Union, Turkey, the United Kingdom and Yugoslavia attended negotiations at Montreux, Switzerland, which began on 22 June 1936. Two major powers were notably absent: Italy, whose aggressively expansionist policies had prompted the conference, refused to attend, and the increasingly isolationist United States declined even to send an observer.
Turkey, the United Kingdom and the Soviet Union each put forward their own set of proposals, each aimed chiefly at protecting the proponent's own interests. The British favoured the continuation of a relatively restrictive approach, the Turks sought a more liberal regime that reasserted their control over the Straits, and the Soviets proposed a regime that would guarantee absolute freedom of passage. The British, supported by France, sought to exclude the Soviet fleet from the Mediterranean Sea, where it might threaten the vital shipping lanes to India, Egypt and the Far East. In the end, the British conceded some of their requests, but the Soviets succeeded in ensuring that the Black Sea countries, including the Soviet Union, were given exemptions from the military restrictions imposed on non-Black Sea nations. The agreement was ratified by all of the conference attendees with the exception of Germany, which had not been a signatory to the Treaty of Lausanne, and with reservations by Japan, and came into force on 9 November 1936; it was registered with the League of Nations Treaty Series on 11 December 1936.
Britain's willingness to make concessions has been attributed to a desire to avoid Turkey being driven to ally itself with or to fall under the influence of Adolf Hitler or Benito Mussolini. It was thus the first in a series of steps by Britain and France to ensure that Turkey would either remain neutral or tilt towards the Western Allies in the event of any future conflict with the Axis.
Terms
As mentioned in its preamble, the Convention replaced the terms of the Lausanne Treaty of 1923 regarding the Straits. This had dictated the demilitarisation of the Greek islands of Lemnos and Samothrace, along with the demilitarisation of the Sea of Marmara and the Bosporus, the Dardanelles, and the Turkish islands of İmroz, Bozcaada and Tavşan.
The Convention consists of 29 Articles, four annexes and one protocol. Articles 2–7 consider the passage of merchant ships. Articles 8–22 consider the passage of war vessels. The key principle – freedom of passage and navigation – is laid out in articles 1 and 2. Article 1 provides, "The High Contracting Parties recognise and affirm the principle of freedom of passage and navigation by sea in the Straits". Article 2 states, "In time of peace, merchant vessels shall enjoy complete freedom of passage and navigation in the Straits, by day and by night, under any flag with any kind of cargo".
The International Straits Commission was abolished, thereby allowing the full resumption of Turkish military control over the Straits and the refortification of the Dardanelles. Turkey was authorised to close the Straits to all foreign warships during a war or when it was threatened by aggression. Also, Turkey was authorised to refuse transit from merchant ships belonging to countries at war with it.
A number of highly specific restrictions in Article 14 and 18 were imposed on what type of warships are allowed passage. Non-Black Sea powers wishing to send a vessel must notify Turkey 15 days prior to the requested passing, and Black Sea states must notify 8 days prior to passage. Also, no more than nine foreign warships, with a total aggregate tonnage of 15,000 tons, may pass at any one time. Furthermore, no single ship heavier than 10,000 tonnes can pass. An aggregate tonnage of all non-Black Sea warships in the Black Sea must be no more than 45,000 tons, with no one nation exceeding 30,000 tons at any given time, and they are permitted to stay in the Black Sea for at most 21 days. Only Black Sea states may transit capital ships of any tonnage, escorted by no more than two destroyers. Any revision to articles 14 and 18 requires 3/4 majority of signatory countries and must include Turkey.
Under Article 12, Black Sea states are also allowed to send submarines through the Straits with prior notice as long as the vessels have been constructed, purchased or sent for repair outside the Black Sea. The less restrictive rules applicable to Black Sea states were agreed as effectively a concession to the Soviet Union, the only Black Sea state other than Turkey with any significant number of capital ships or submarines. The passage of civil aircraft between the Mediterranean and the Black seas is permitted only along routes authorised by the Turkish government.
Under article 19, warships of countries at war are forbidden passage, except to return to their base.
Implementation
The terms of the convention were largely a reflection of the international situation in the mid-1930s. They largely served Turkish and Soviet interests by enabling Turkey to regain military control of the Straits and assuring Soviet dominance of the Black Sea. Although the Convention restricted the Soviets' ability to send naval forces into the Mediterranean Sea – satisfying British concerns about Soviet intrusion into what was considered a British sphere of influence – it also ensured that outside powers could not exploit the Straits to threaten the Soviet Union.
World War II
This feature was to have significant repercussions during World War II; the Montreux regime prevented the Axis powers from sending naval forces through the Straits to attack the Soviet Union. The Axis powers, thereby, were severely limited in naval capability for their Black Sea campaigns, relying principally on small vessels transported overland by rail and canal networks. Six U-boats of the German 30th U-boat Flotilla reached the Black Sea in 1942 after a transport from North Sea via Elbe, over land and the Danube to be operated from the harbours of Constanţa and Feodosiya from 1942 to 1944.
Auxiliary vessels and armed merchant ships comprised a grey area, though, and the transit of such Axis vessels through the straits led to friction between the Allies and Turkey. After a number of German auxiliary ships had been permitted to transit the Straits, repeated protests from Moscow and London prompted the Turkish government to ban passage of "suspicious" Axis ships from June 1944.
Aircraft carriers
Although the Montreux Convention is cited by the Turkish government as prohibiting aircraft carriers from transiting the Straits, the treaty actually contains no explicit prohibition on aircraft carriers. However, modern aircraft carriers are heavier than the 15,000-ton limit imposed on warships, which makes it impossible for non–Black Sea powers to transit modern aircraft carriers through the Straits.
Under Article 11, Black Sea states are permitted to transit capital ships of any tonnage through the straits, but Annex II specifically excludes aircraft carriers from the definition of capital ship. In 1936, it was common for battleships to carry observation aircraft. Therefore, aircraft carriers were defined as ships that were "designed or adapted primarily for the purpose of carrying and operating aircraft at sea". The inclusion of aircraft on any other ship does not classify it as an aircraft carrier.
The Soviet Union designated its Kiev-class and Kuznetsov-class ships as "aircraft-carrying cruisers" because the ships were armed with P-500 and P-700 cruise missiles, which also form the main armament of the Slava-class cruiser and the Kirov-class battlecruiser. The result was that the Soviet Navy could send its aircraft-carrying cruisers through the Straits in compliance with the convention, but at the same time, the Convention denied access to NATO aircraft carriers, which exceeded the 15,000-ton limit. While the Soviet Union built its aircraft-carrying cruisers in the Black Sea, neither the Soviet Union nor Russia has ever based them in the Black Sea.
Turkey chose to accept the designation of the Soviet aircraft carrying cruisers as aircraft cruisers, as any revision of the convention could leave Turkey with less control over the Straits, and the UN Convention on the Law of the Sea had already established a more liberal passage through other straits. By allowing the Soviet aircraft-carrying cruisers to transit the Straits, Turkey could leave the more restrictive Montreux Convention in place.
Controversies
Istanbul Canal
If it comes to fruition, the long-proposed Istanbul Canal (Kanal Istanbul) project could, according to Turkey, circumvent the Montreux Convention in the 21st century and allow greater Turkish autonomy with respect to the passage of military ships, which are limited in number, tonnage, and weaponry, from the Black Sea to the Sea of Marmara. The canal project would involve building a 45 km (28 mi) artificial waterway through Thrace to connect the Sea of Marmara with the Black Sea. That route would run nearly parallel to the Bosporus, but ships transiting it would arguably not be subject to the terms of the Montreux Convention. Currently, the Dardanelles is heavily congested with shipping and there are long waits to pass through the Bosporus. The Canal project's stated purposes are to speed up shipping and boost revenue by providing another maritime route.