Does the Montreux Convention Have an End Date? Article 28, Denunciation and Why the Turkish Straits Regime Still Stands

Why It Matters

The 1936 Montreux Convention has no fixed expiry date. Its original 20-year term ran out in 1956, and under Article 28 it has continued in force since, ending only two years after a signatory gives notice of denunciation. No party has ever done so. Claims that the regime 'ends' in 2036 misread the text.

Readers meeting a headline about a Montreux 'end date' should check it against the treaty itself. The only mechanisms the text provides are denunciation on two years' notice (Article 28) and a formal revision procedure (Article 29). Neither has altered the Convention's core provisions.

Background

The Montreux Convention Regarding the Regime of the Straits was signed on 20 July 1936 in Montreux, Switzerland, and entered into force on 9 November 1936. It replaced the 1923 Lausanne Straits Convention, restored Türkiye's sovereign control over the Bosphorus, Sea of Marmara and Dardanelles, and allowed remilitarization of the Straits zone.

What Is the 1936 Montreux Convention (and What Is Montreux)?

'Montreux' is shorthand for this treaty, named after the Swiss lakeside town where the conference met in June and July 1936. The 1923 Lausanne arrangement had demilitarized the Straits and placed their supervision under an international commission. In 1936 Türkiye asked the signatories of that arrangement to revise it, citing the changed security environment in Europe.

The Convention was concluded by Bulgaria, France, Greece, Japan, Romania, Türkiye, the United Kingdom (together with Australia and India), the Soviet Union and Yugoslavia. Italy did not take part in the conference and acceded later. It was registered in the League of Nations Treaty Series, which is the authoritative source for the text. For the full operating logic, see our companion guide on what is the Montreux Convention and how does it affect the Black Sea.

Does the Montreux Convention Have an End Date? Article 28 Explained

Article 28 provides that the Convention remains in force for twenty years from its entry into force. If, two years before that period expired, no party had given notice of denunciation to the French Government, the Convention continues in force until two years after such notice is eventually given. No notice came before the first term ended, so it rolled forward and has no scheduled end.

This is why popular ideas of a 'centenary expiry' or a 'sunset in 2036' have no textual basis. A hundred-year anniversary is not mentioned in the treaty. The same applies to confusion with 2023, the centenary of the Lausanne Treaty of 24 July 1923: that anniversary did not end any Lausanne instrument either, and it has no bearing on Montreux.

How Can It Be Changed? Denunciation, Revision and Practice

The Convention offers two formal routes and one informal one. They differ sharply in trigger and effect.

Under Article 29, each party may initiate an amendment proposal at the expiry of every five-year period from entry into force. A proposal must be supported by one other party if it concerns Article 14, or by two other parties for any other article, and must be notified three months before the period ends. If diplomacy fails, parties undertake to send delegates to a conference. Decisions there require unanimity, except for Article 14, which needs a three-quarters majority that includes three-quarters of the Black Sea powers, Türkiye among them.

Informal practice matters because the Convention entrusts implementation to Türkiye as territorial sovereign. A well-known example is the 1970s transit of Soviet Kiev-class ships, which Türkiye admitted as aircraft-carrying cruisers, since the Convention excludes aircraft carriers from passage. That was an interpretation, not an amendment. The core 1936 provisions have not been amended.

What Does the Convention Actually Regulate?

The text sets out the following, which readers should verify against the treaty itself:

• Peacetime commercial passage: merchant ships of all flags enjoy freedom of transit and navigation, subject to the Convention's sanitary and administrative rules.
• Warships of non-Black Sea states: limits on the size of vessels, on aggregate tonnage and on the length of stay in the Black Sea (Article 18), with prior notification to Türkiye through diplomatic channels.
• Black Sea littoral states: a special position, including transit rights for certain larger vessels and for submarines returning from construction or repair outside the Black Sea, under conditions set in the text.
• Wartime, Türkiye neutral (Article 19): belligerent warships may not pass, subject to limited exceptions, including return to home base.
• Türkiye at war or under threat (Articles 20 and 21): Türkiye gains discretion over passage, and Article 21 lets it apply that discretion if it considers itself threatened with imminent danger of war.

How Did It Operate During the Russia–Ukraine War?

In late February 2022, following Ukraine's request and after Russia's invasion began, Türkiye characterized the situation as a war and stated it would apply the wartime provisions. Foreign Minister Mevlüt Çavuşoğlu announced that the Straits would be closed to warships of belligerent states, riparian or not, with the exception for vessels returning to their home bases. Commercial traffic through the Straits continued.

The mechanism later supported the diplomacy described in Russia–Ukraine Mediation and the Black Sea Grain Initiative. For a sister-publication view of how the regime has held since, see Archive of Nations on the Montreux Convention in the Russia–Ukraine War.

What Would Happen If a Party Tried to Abandon It?

On the text of Article 28, notice by any one party is the trigger, and it takes effect only after two years. The wording points to the termination of the regime as a whole, not a single party's exit, and it envisages a conference to conclude a new convention. That makes denunciation an extreme step.

No party has taken it, in part because every actor gains something from the current balance. Debate in April 2021 over whether Türkiye might leave Montreux ended with Turkish officials saying there was no intention to withdraw.

Key Players & Positions

No signatory has formally proposed denouncing the Montreux Convention, but Russia, Ukraine, NATO members and Türkiye read its practical effects differently. Russia stresses limits on non-Black Sea navies, Ukraine and many Western states favor strict wartime closure, and Türkiye administers the text as territorial sovereign. The debate concerns interpretation, not abandonment.

• Russia: Russian officials and commentators have generally supported keeping the regime, emphasizing its limits on the presence of non-littoral navies. Russian commentary has also pointed to the return-to-base exception when discussing movement of its fleet.
• Ukraine: Kyiv asked Türkiye in February 2022 to apply the Convention's closure provisions, and has since favored strict enforcement of Article 19.
• NATO and Western states: Governments have generally welcomed Türkiye's implementation. Some analysts argue the tonnage and duration limits constrain allied naval presence in the Black Sea, and some call for new maritime arrangements, though no government has made a formal revision proposal.
• Black Sea littoral states (Bulgaria, Romania): They favor a stronger allied posture in the region but have worked within Montreux rather than seeking to reopen it.
• Analysts calling for revision: A minority argues that 1936 rules do not fit modern technology such as drones and long-range missiles. Others reply that reopening Article 14 or Article 18 could produce a worse bargain for every party. For an independent analysis, see Horizon Politics on whether the Montreux regime will hold after the Russia–Ukraine war and Diplomacy Arena on Montreux and Türkiye's mediation.

Source Comparison

Western, Russian and Turkish sources agree the Montreux Convention is in force, but framings of its duration differ. Some commentary treats 2036, the treaty's centenary, or 2023, the Lausanne centenary, as an expiry date. The treaty text and Ankara's Foreign Ministry say otherwise: Article 28 sets no end date, only a two-year denunciation notice.

Readers can compare this approach with our wider fact check of Türkiye claims in international media and the standards in Editorial Principles.

Key Terms & Related Guides

Key terms in the Montreux debate include the Turkish Straits, denunciation, revision, belligerent, littoral state and tonnage limits. Each has a specific meaning in the 1936 text, and confusing denunciation with revision is the commonest source of 'expiry' myths. The definitions below, with related guides, anchor the article's treaty-law reading.

• Turkish Straits: the Bosphorus, the Sea of Marmara and the Dardanelles, which link the Black Sea to the Aegean and the Mediterranean.
• Denunciation: formal notice by a party under Article 28 that starts a two-year period.
• Revision: amendment through the Article 29 procedure, not the same as ending the treaty.
• Belligerent: a state at war; the Convention treats belligerent warships differently from peacetime traffic.
• Littoral state: a state with a Black Sea coast, which receives specific transit provisions.
• Tonnage limits: the caps on single-vessel and aggregate warship tonnage for non-Black Sea states set in Articles 14 and 18.

For further reading:

• What is the Montreux Convention and how does it affect the Black Sea
• Black Sea Grain Initiative Türkiye mediation Istanbul talks
• Türkiye's maritime jurisdiction explained
• Fact check Türkiye claims in international media
• About The Political Accord

The Political Accord Editorial Team

The Political Accord presents global affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy as stated by Turkish government sources.