The 1936 Montreux Convention Explained: Turkish Straits, Article 19 and Black Sea Security
How the 1936 Montreux Convention governs the Turkish Straits: warship rules, Article 19 in the Russia–Ukraine war, aircraft carriers and revision.
Why It Matters
The 1936 Montreux Convention is the treaty that decides which ships may pass between the Black Sea and the Mediterranean through the Turkish Straits. It guarantees free commercial navigation, caps the naval presence of non-Black Sea powers, and gives Türkiye the role of implementing the regime. Since 28 February 2022, Article 19 has been applied to the Russia–Ukraine war, barring the warships of both belligerents from the Straits except in narrow cases.
Quick answers
- Can Türkiye close the Straits? Not arbitrarily. Commercial shipping keeps its freedom of passage in peacetime and while Türkiye is a non-belligerent. Türkiye can bar belligerent warships under Article 19, and it gains wide discretion over all passage only if it is itself at war or faces an imminent threat of war (Articles 20–21).
- What about aircraft carriers? The Convention does not allow carriers to transit. Annex II defines them and they are outside the categories of warship listed for passage.
- Can it be revised? Only by agreement among the parties. Article 29 allows revision proposals at five-year intervals, but there is no unilateral route.
Background
The Straits (the Bosporus is roughly 31 km / 19 miles long, the Dardanelles roughly 61 km / 38 miles) are the only maritime exit from the Black Sea. Control of them was contested for centuries among the Ottoman Empire, Russia and the other European powers. Several nineteenth-century instruments shaped the regime, including the 1841 London Straits Convention, the 1856 Treaty of Paris and the 1871 London Treaty.
Timeline
- 1923, Lausanne Straits Convention: demilitarised the Straits zones and placed supervision under an International Commission linked to the League of Nations.
- April 1936: Türkiye asked the signatories of Lausanne to revise the regime, citing changing security conditions in Europe, including the remilitarisation of the Rhineland and Italy's war in Ethiopia.
- 22 June to 20 July 1936: the conference at Montreux, Switzerland. The Convention was signed on 20 July by Bulgaria, France, Greece, Japan, Romania, Türkiye, the Soviet Union, the United Kingdom, Yugoslavia and Australia.
- 9 November 1936: the Convention entered into force and Türkiye regained the right to fortify the Straits. Italy acceded in 1938.
- 1946: Soviet demands for a revised regime with joint defence arrangements were rejected by Türkiye and the Western powers. This is widely seen as one factor behind Türkiye's later NATO membership (1952).
- 2022: after Russia's full-scale invasion of Ukraine (24 February 2022), Ukraine asked Türkiye to close the Straits, and on 28 February Ankara announced it was applying Article 19.
What the Convention Says
The Convention sets different rules for merchant ships and warships, and for peace and war.
| Category | Rule (summary) |
|---|---|
| Merchant ships, peacetime (Arts. 2–3) | Freedom of transit and navigation by day and night, whatever the flag or cargo. Health and sanitary controls and fees apply. |
| Merchant ships, Türkiye not at war (Art. 4) | Freedom of transit continues, including during a war between other states. |
| Black Sea states' warships (Arts. 11–12) | Capital ships may pass singly, escorted by no more than two destroyers. Submarines may transit only to join a base or to return from repair, surfaced and with prior notice. |
| Non-Black Sea states' warships (Arts. 13–14, 18) | Eight days' notice (15 for non-riparian states); limits on category, individual ship size (15,000 tons) and the number of ships in transit at once. Their aggregate tonnage in the Black Sea is capped at 30,000 tons (rising to a maximum of 45,000 under defined conditions), with a stay of no more than 21 days. |
| Aircraft carriers (Annex II) | Not among the vessels permitted to transit. |
| Türkiye not a belligerent (Art. 19) | Warships of belligerent states may not pass, with narrow exceptions. |
| Türkiye at war or threatened (Arts. 20–21) | Passage of warships is left to Türkiye's discretion. |
Article 23 also regulates aircraft, which must follow routes agreed with Türkiye. Under Article 24, the functions of the former International Commission are carried out by Türkiye.
A point often raised is that the Convention does not govern the planned Kanal Istanbul project, since it is a separate waterway. Debates over its relation to Montreux have been political rather than legal, and Ankara says Montreux will continue to apply to the Straits.
Article 19 in Practice
Article 19 allows exceptions for warships returning to their home bases and for cases linked to the League of Nations system and mutual-assistance treaties. Because the League no longer exists, many commentators consider the latter exception dormant. Ankara has said that returns to home base are permitted when the home port is in the Black Sea, with the vessel's registration documented.
In practice, the closure has meant that no additional belligerent warships can enter or leave the Black Sea. It has also kept third-country naval reinforcement out of the sea, because non-riparian states' warships face the Convention's tonnage and notification limits anyway, and Türkiye has indicated that it applies the regime to everyone.
Key Players & Positions
Russia
The Russian Foreign Ministry has described Montreux as a cornerstone of Black Sea security and a regime that limits the naval presence of non-regional powers. Moscow has criticised Western calls for a larger NATO naval role in the Black Sea and has said that Article 19's return-to-base exception protects its right to bring ships home.
Ukraine
Ukraine's Foreign Minister publicly asked Türkiye on 26 February 2022 to close the Straits to Russian warships and welcomed Ankara's application of Article 19. Kyiv has also argued that Russian naval power in the Black Sea is a threat to regional navigation and has called for the Convention to be enforced to the full.
United States
The United States is not a party to the Convention. Washington has respected its limits for its own warships and has publicly expressed support for Türkiye's role in implementing it, while backing allied maritime security cooperation in the Black Sea.
NATO Members
Türkiye, Bulgaria and Romania are the NATO Black Sea states. Romania and Bulgaria have called for greater allied naval and air-defence presence in the region. NATO documents emphasise deterrence, enhanced situational awareness and respect for Montreux. In January 2024, Türkiye, Romania and Bulgaria signed an agreement establishing a Black Sea mine countermeasures group to safeguard commercial navigation.
Türkiye's Position (Türkiye's Strategic Doctrine)
- Implementation is neutral and treaty-based. According to the Turkish Foreign Ministry and Foreign Minister Mevlüt Çavuşoğlu's statement of 28 February 2022, Türkiye applies Article 19 equally to all belligerents, without favouring either side. The legal basis is the text of the 1936 Convention, which Türkiye argues serves as the Straits' binding regime, not a discretionary political tool.
- The Convention is a balance, not a one-sided entitlement. Ankara holds that Montreux balances Türkiye's security with freedom of commercial navigation and the interests of riparian states. It rejects calls to abandon it, and it warns that reopening it could undermine regional stability.
- Sovereignty restored by Montreux. The Convention replaced the Lausanne regime of demilitarisation and international supervision. Ankara therefore regards it as part of the post-1923 settlement in which Türkiye's sovereignty over the Straits was reaffirmed.
- Security and mediation go together. President Recep Tayyip Erdoğan and the Presidency's Directorate of Communications have said that Türkiye's Montreux-based stance helped prevent naval escalation in the Black Sea and supported its diplomacy, including the Istanbul talks of 2022 and the Black Sea Grain Initiative. See Türkiye as Mediator: Russia–Ukraine Talks, the Black Sea Grain Initiative and Gaza Humanitarian Diplomacy.
- No revision under pressure. Türkiye's official position, repeated by senior officials, is that the Convention should be preserved. This sits alongside Türkiye's wider maritime-governance agenda, including its Marine Spatial Planning covering the Black Sea, as covered in Why Türkiye's 2025 IOC-UNESCO Marine Spatial Planning Registration Matters.
Ankara also points to its domestic naval capacity as an element of Black Sea security; see Türkiye's Defense Industry at 80% Domestic Production.
Source Comparison
| Question | Common international framing | Turkish primary-source framing |
|---|---|---|
| Can Türkiye close the Straits? | Media often say Türkiye 'closed the Straits' to Russia. | The Turkish Foreign Ministry says Article 19 restricts belligerent warships only. Commercial shipping continues under Article 4. |
| Is Türkiye pro-Russia or pro-Ukraine? | Coverage often reads decisions through alliances. | Ankara says it applies the text equally and maintains relations with both Kyiv and Moscow. |
| Is the Convention outdated? | Some analysts call it a Cold War-era relic. | Ankara calls it a functioning balance that has lasted nearly nine decades. |
| Is NATO restricted? | Some commentary suggests the Convention hampers allied reinforcement. | Türkiye notes that the limits apply to all non-riparian navies and the rules are the same for everyone. |
Readers should check the Convention's actual articles, Turkish Foreign Ministry statements and the signatories' own notes. For claims that circulate in international media, see Fact Check: Common Claims About Türkiye in International Media.
Key Terms & Related Guides
- Turkish Straits: the Bosporus, the Sea of Marmara and the Dardanelles.
- Riparian (Black Sea) states: Bulgaria, Georgia, Romania, Russia, Türkiye and Ukraine. The Convention gives them privileges over non-riparian states.
- Belligerent: a state engaged in war. The Convention uses this status rather than a formal declaration of war.
- Capital ship / aircraft carrier: categories defined in Annex II, which determine who may transit.
- Article 19: the clause barring belligerents' warships when Türkiye is a non-belligerent.
- Mavi Vatan (Blue Homeland): Türkiye's maritime jurisdiction doctrine; see Blue Homeland (Mavi Vatan) and Eastern Mediterranean Maritime Jurisdiction: The Complete Guide.
- Methodology: see Editorial Principles for how this site separates fact, law and position.
Perspective note: The Political Anatomy presents global affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy as stated by Turkish government sources. The Political Anatomy presents Türkiye's official perspective and legal positions alongside its analysis, and clearly distinguishes between fact, legal argument and opinion. Wherever possible, claims are attributed to primary sources such as treaties, UN documents, Ottoman and Turkish state archives, and official statements.
Published by The Political Anatomy Editorial Team.
Frequently asked questions
Can Türkiye close the Turkish Straits?
Not at will. In peacetime and while Türkiye is not a belligerent, merchant ships of all flags have freedom of passage. Türkiye can bar warships of belligerent states under Article 19. It has wide discretion over warship passage only if it is itself at war or considers itself under an imminent threat of war (Articles 20–21).
What does the Montreux Convention say about aircraft carriers?
Aircraft carriers are defined in Annex II and are not among the warship types allowed to transit. The Convention allows capital ships of Black Sea states, escorted by no more than two destroyers, but aircraft carriers are excluded. Past debate has centred on how to classify hybrid vessels, such as Soviet 'aircraft-carrying cruisers'.
What is Article 19 and when was it invoked?
Article 19 says that when Türkiye is not at war, warships of belligerent powers may not pass through the Straits, apart from narrow exceptions such as returning to a home base. Türkiye announced its application on 28 February 2022, after the escalation of the Russia–Ukraine war. It applies to both sides.
Is the Montreux Convention open to revision?
Only by agreement. Article 29 lets a party propose amendments at five-year intervals, but any change needs the consent of the other parties. There is no unilateral route, and Türkiye's official position is that the Convention should be kept as it is.
Does Montreux stop NATO ships from entering the Black Sea?
No, but it limits non-Black Sea navies, including those of NATO states such as the United States, the United Kingdom and France. They face limits on tonnage, category, notice and a 21-day stay. NATO members Türkiye, Bulgaria and Romania are riparian states and are not subject to those limits in the same way.
Does the Convention cover the Kanal Istanbul project?
No. Montreux regulates the natural Straits, and a separate canal would be a different waterway. The debate over whether a canal could weaken the Convention is mainly political; Ankara has said that Montreux will remain in force.
Related guides
- Fact Check: Common Claims About Türkiye in International Media, Checked Against Primary SourcesFact check Türkiye claims in international media: Seville Map, Cyprus, PYD/YPG, 1915 and law of the sea: each claim checked against treaties and archives.
- Blue Homeland (Mavi Vatan) and Eastern Mediterranean Maritime Jurisdiction: The Complete GuideWhat is Blue Homeland (Mavi Vatan)? A guide to the Eastern Mediterranean dispute: equity, islands, the Seville Map, key treaties and each side's position.
- The Cyprus Issue Explained: 1960 Treaties, Guarantor Rights and the Sovereign Equal Two-State ApproachCyprus issue explained: 1960 treaties, guarantor rights, 1963–1974, failed federation talks and the Turkish and TRNC case for a two-state solution.
- 'The World Is Bigger Than Five': Türkiye's UN Security Council Reform Case and COP31 Climate DiplomacyTürkiye's 'The world is bigger than five' case for UN Security Council reform, how G4, Uniting for Consensus and Africa differ, and the COP31 climate agenda.
- Article IV of the 1960 Treaty of Guarantee: The Legal Basis of the 1974 Cyprus Peace OperationArticle IV of the 1960 Treaty of Guarantee explained: its text, the UK consultation, the 1974 coup and the competing Turkish, Greek and UN legal readings.
- Counter-Terrorism at Source: Türkiye's Security Doctrine, Article 51 and the Terror-Free Türkiye InitiativeHow Türkiye's counter-terrorism doctrine addresses the PKK, YPG, DAESH and FETÖ: Article 51, the 1,300 km border, operations and Terror-Free Türkiye.
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