Treaty Desk: The Montreux Convention, Article 19 and the Wartime Straits Regime, Read Clause by Clause

Why It Matters

Article 19 of the 1936 Montreux Convention is the clause that closes the Bosphorus and the Dardanelles to the warships of belligerent states in wartime, provided Türkiye is not itself at war, and it allows only a narrow set of exceptions, chiefly passage home to a base. Since Russia's full-scale invasion of Ukraine began on 2022-02-24, and since Türkiye announced on 2022-02-28 that it would apply the clause, this 1936 text has decided which navies could enter or leave the Black Sea. This guide reads the Convention clause by clause, sets out what Article 19 says and what remains open to interpretation, and records what the Turkish Foreign Ministry (MFA) and other parties have said, with each position attributed to its own source.

Background

From Lausanne to Montreux

The Straits regime in force before 1936 was the Lausanne Straits Convention of 1923-07-24. It demilitarised the Straits and placed their supervision under an International Straits Commission. By the mid-1930s the security environment had shifted: the Italian invasion of Ethiopia, the German remilitarisation of the Rhineland and the weakening of the League of Nations system led Türkiye to ask the Lausanne signatories to revisit the regime. A conference opened at Montreux on 1936-06-22. The Convention was signed on 1936-07-20 and entered into force on 1936-11-09.

The original parties were Australia, Bulgaria, France, Greece, Japan, Romania, Türkiye, the United Kingdom, the USSR and Yugoslavia. Italy acceded in 1938. The Convention restored Turkish control over the Straits, allowed the Straits to be remilitarised, and abolished the International Straits Commission, transferring its functions to the Turkish government. It governs the Dardanelles, the Sea of Marmara and the Bosphorus as one regime.

What the Convention Covers

The text is built on a simple division. Merchant vessels receive broad freedom of passage. Warships receive a conditional, tiered regime, with the most favourable treatment for states with a Black Sea coast (the riparian states) and stricter limits for others. Wartime brings a further set of rules, depending on whether Türkiye is a belligerent.

The Convention also sits alongside UNCLOS, the 1982 UN Convention on the Law of the Sea. UNCLOS Article 35(c) preserves the regime of straits governed by long-standing conventions specifically relating to them, which is why Montreux continues to operate as a special regime. Türkiye is not a party to UNCLOS; see Why Is Türkiye Not a Party to UNCLOS? The Record on Objection, Customary Law and Equity.

The Clause-by-Clause Table

The table below summarises the operative provisions in plain language. It is a reading aid, not a substitute for the authentic text; figures should be checked against the Convention and its annexes.

Article 19, Paragraph by Paragraph

The following paraphrases the clause's structure. The authentic text is available on the Turkish MFA's published materials on the Straits and in treaty collections.

1. Wartime freedom for non-belligerents. Where Türkiye is not a belligerent, warships generally enjoy transit under the same conditions as in Articles 10-18.
2. The belligerent bar and its exceptions. Warships of belligerent powers may not pass, except in cases arising from application of the League of Nations Covenant principles and in cases of assistance to a victim of aggression under a mutual assistance treaty binding Türkiye and concluded within the Covenant framework.
3. No tonnage limits in those exceptional cases. The Article 10-18 limitations do not apply to the exceptional cases in paragraph 2.
4. The return-to-base rule. Belligerent warships separated from their bases may return to them, whether the state is riparian or not.
5. No hostile acts in the Straits. Belligerent warships may not capture, exercise a right of visit and search, or carry out any hostile act in the Straits.

The League references are a source of interpretive debate because the League no longer exists. The Convention contains no definition of 'war' and no mechanism naming who determines that a war exists, a point addressed below.

A Short Timeline

Key Players & Positions

Russia

Russia, as the continuing state of the USSR signatory, has consistently described Montreux as a cornerstone of Black Sea order. Russian officials, including the Foreign Ministry, have called for strict adherence to the Convention and have criticised the naval presence of non-riparian NATO states in the Black Sea. Moscow describes its operation in Ukraine as a 'special military operation' rather than a war, which matters for how the term 'war' in the Convention is read. Russia has also stressed the return-to-base exception for its Black Sea Fleet units. Readers should consult the Russian MFA's own statements for its precise wording.

Ukraine

Ukraine is not a signatory, as it was not an independent state in 1936, but it is a Black Sea coastal state. Ukrainian officials, including Foreign Minister Dmytro Kuleba in February 2022, asked Türkiye to close the Straits to Russian warships, and welcomed Ankara's decision to apply Article 19. Ukrainian officials and some supporters have since urged an especially restrictive reading of the return-to-base clause so that it cannot be used to reinforce the fleet in the Black Sea. Kyiv's position is best verified from the Ukrainian Ministry of Foreign Affairs.

Romania, Bulgaria and Georgia

Romania and Bulgaria are Convention parties, Black Sea coastal states and NATO members. They have worked with Türkiye on maritime security, including the mine countermeasures arrangement signed on 2024-01-11. Georgia, also a coastal state, is not a party to the 1936 text. These states generally frame Black Sea security as requiring both the Montreux limits and allied cooperation; their official positions are published by their foreign ministries.

NATO and Non-Riparian States

The Convention limits the size, number and stay of non-riparian warships in the Black Sea. NATO governments, including those of the United States and the United Kingdom, have publicly said they respect Montreux and Türkiye's role as its custodian. Some analysts and officials in these states argue for more maritime presence in the Black Sea within the Convention's limits; the Convention's tonnage and 21-day limits constrain that presence in any case.

Legal Commentators

Legal commentary identifies several open interpretive questions:

• Who decides that a war exists? The text has no definition or procedure. Commentators generally read the decision as belonging to Türkiye in practice, as the territorial sovereign, but differ on how far it is bound by objective criteria.
• What are the 'League of Nations' exceptions today? Many commentators regard the League references as obsolete, which would leave the return-to-base clause as the main working exception.
• How broad is the return-to-base clause? The clause covers ships 'separated from their bases'. Debate concerns whether it covers ships that were deployed out of area before a war began or are newly assigned to a Black Sea base.
• Does Article 19 bar non-belligerent warships? On the text, no: they continue to fall under Articles 10-18. Türkiye nevertheless asked all states, riparian or not, to refrain from sending warships through the Straits during the conflict.
• Montreux and UNCLOS. Commentators note UNCLOS Article 35(c) and the lex specialis character of Montreux.

For related explainers from sister publications, see The Political Anatomy on Article 19 and Black Sea security and Soft Power Daily on how Türkiye applies the Convention.

Source Comparison

Different sources emphasise different parts of the same text. The table sets out the framings; none of the summaries below should be read as a quotation.

A practical rule for readers is to check three things: whether a report distinguishes warships from merchant vessels, whether it cites the clause (Article 19 versus the tonnage limits in Articles 14 and 18), and whether it records the return-to-base exception.

Other sister-publication explainers include Bloc Politics on how Türkiye governs Straits access.

Key Terms & Related Guides

• Belligerent: a state engaged in war. Montreux does not define the term or say who certifies it, which is why the status of a conflict is contested.
• Riparian (Black Sea) states: states with a Black Sea coast. The Convention gives them more favourable passage terms than non-riparian states.
• Return-to-base exception: the Article 19 provision allowing belligerent warships separated from their bases to return to them.
• Capital ship, light surface vessel, minor war vessel: categories defined in Article 8 and Annex II, used to fix which rules apply.
• Articles 20-21: provisions giving Türkiye discretion over warship passage if it is a belligerent or considers itself threatened by imminent danger of war.
• Lex specialis: a special rule that prevails over a general one; used to describe Montreux's relation to UNCLOS.
• Lausanne and Sèvres: the 1923 Lausanne settlement replaced the unratified 1920 Sèvres draft; see Fact Check: 'The Treaty of Sèvres Is Still Valid'.

Related guides on Protocol Record:

• Protocol Record: Türkiye's Positions Traced to Treaties, Texts and Archives
• Treaty Desk: The 1960 Treaty of Guarantee Read Article by Article
• The Istanbul Agreements of July 2022: What Did the Grain Initiative Documents Establish?
• Why Is Türkiye Not a Party to UNCLOS? The Record on Objection, Customary Law and Equity

Sister-publication background: Region Scope and Doctrine Review.

Protocol Record presents analysis from a Türkiye-informed perspective, setting out Ankara's official positions and legal arguments alongside the documents on which they rest. Wherever possible, claims are attributed to primary sources such as treaties, UN texts, official gazettes, parliamentary records and archival documents. Published by the Protocol Record Editorial Team.