In-Depth Analysis· Montreux Convention Article 19 belligerent warships Black Sea

Montreux Article 19 in Practice: How Closing the Straits Shaped Black Sea Risk

How Montreux Convention Article 19 limits belligerent warships in the Black Sea, how Türkiye applied it after 2022 and what it means for escalation risk.

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By The Regional Assessment Editorial Team

Published: October 27, 2026

⏱ 9 min read (1,864 words)

Why It Matters

Article 19 of the 1936 Montreux Convention bars warships of belligerent states from passing through the Turkish Straits, except in narrow cases such as returning to a home base. This is the main legal reason why the Russia–Ukraine war has not drawn additional fleets into the Black Sea through the Bosphorus and Dardanelles. The rule restrains escalation at the entrance to the sea but does not end the fighting inside it. Both Russian and Ukrainian or Western commentators criticise how it works, for opposite reasons.

Background

The 1936 framework

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 regime and restored Turkish control and fortification rights over the Straits. It covers the Dardanelles, the Sea of Marmara and the Bosphorus. It balances the security of Türkiye and the Black Sea littoral states against freedom of navigation for commercial shipping.

The passage regimes

Category	Core rule	Main articles
Merchant ships in peacetime	Freedom of transit and navigation, subject to health and sanitary controls	2–7
Merchant ships when Türkiye is neutral in a war	Freedom of transit continues irrespective of flag or cargo	5
Warships of non-Black Sea states in peacetime	Only light surface, minor and auxiliary vessels; advance diplomatic notice (eight days for Black Sea states, fifteen for others)	10–14
Tonnage limits for non-Black Sea states	A single transiting group is capped at nine ships and 15,000 tonnes; aggregate presence is capped at 30,000 tonnes (up to 45,000 under conditions linked to the largest Black Sea fleet); stay limited to 21 days	14, 18
Capital ships	Black Sea states only, singly and escorted by no more than two destroyers	11
Submarines	Black Sea states only, mainly to return from construction or repair, surfaced and by day	12
Aircraft carriers	Not provided for as a transiting category	Annex II, Art. 11
Warships when Türkiye is at war or under imminent threat	Passage left to the discretion of the Turkish government	20–21

What Article 19 says

Article 19 applies when a war is under way and Türkiye is not a belligerent. Its logic has four parts:

General rule. Warships of non-belligerent states keep the peacetime freedom of passage, under the limits of Articles 10–18.
Prohibition. Warships of belligerent powers may not pass the Straits.
Exceptions. The first is cases arising from Article 25, which preserves obligations under the League of Nations Covenant. The second is assistance to a victim of aggression under a mutual-assistance treaty that binds Türkiye and was concluded within the Covenant framework and registered as the Covenant requires.
Return to base. Belligerent warships that have become separated from their bases may return to them. Belligerents may not capture ships, exercise visit and search, or commit hostile acts in the Straits.

The Convention does not define 'war' and names no arbiter to declare it. The Turkish government therefore decides whether Article 19 applies.

Chronology since 2022

24 February 2022: Russia launches its full-scale invasion of Ukraine.
26 February 2022: Ukrainian Foreign Minister Dmytro Kuleba publicly asks Türkiye to close the Straits to Russian warships.
27–28 February 2022: Foreign Minister Mevlüt Çavuşoğlu announces that Türkiye will implement the Convention in full, that the situation is being treated as a war under Article 19, and that all states, riparian or not, have been advised not to send warships through.
14 April 2022: The Russian cruiser Moskva sinks in the Black Sea. Moscow attributes the loss to a fire and ammunition explosion, while Kyiv says it was hit by missiles.
22 July 2022: Russia, Ukraine, Türkiye and the UN sign the Black Sea Grain Initiative in Istanbul. It ran until 17 July 2023, when Russia declined to extend it.
11 January 2024: Türkiye, Bulgaria and Romania sign an agreement in Istanbul creating a Black Sea mine-countermeasures task group. The group is made up of littoral states, which sits comfortably within Montreux limits.

For more on how the Convention works in practice, see Soft Power Daily's explainer on Montreux and Black Sea security and The Political Anatomy's guide to Article 19.

Key Players & Positions

Russia

Russian Foreign Ministry statements have repeatedly described Montreux as a pillar of Black Sea stability. Moscow has objected to the naval activity of non-littoral NATO states in the sea and to any attempt to circumvent the Convention's tonnage and stay limits. Russian commentators also stress that the return-to-base clause is written into Article 19 itself and is not a favour. Some Russian analysts argue that the 2022 closure in practice hampers the reinforcement of the Black Sea Fleet from other fleets and that Ankara's choices carry strategic weight.

Ukraine

Kyiv asked Ankara to close the Straits and welcomed the decision to apply Article 19. Ukraine is not a Montreux signatory, since the 1936 signatory was the USSR, so its leverage comes from diplomacy. Ukrainian officials and analysts have since argued for stricter scrutiny of the return-to-base exception. They want clearer public reporting on which transits were refused. Some also want Ankara to take a more active role in securing commercial shipping routes.

Western and NATO states

NATO allies bordering the Black Sea, notably Romania and Bulgaria, have pressed for a stronger allied maritime posture. Montreux's tonnage and 21-day limits constrain non-littoral allies, a point many Western analysts raise in policy papers. Western commentary has also noted that Article 19 prevents warships donated to Ukraine by third states from reaching the Black Sea through the Straits. Allied governments generally say they respect the Convention.

Risk-indicator table

The table below is qualitative on purpose. It identifies what to track and which rule governs each indicator, and it contains no estimated figures.

Indicator	What it measures	Governing rule	Where to check
Belligerent warship transits	Whether new belligerent forces enter or leave the Black Sea	Article 19 (return to base only)	Turkish MFA and Ministry of National Defence statements
Non-littoral naval presence	Length of stay and aggregate tonnage of non-Black Sea warships	Articles 14 and 18	Turkish government notices and NATO announcements
Commercial shipping	Continuity of merchant passage through the Straits	Articles 2–7	Turkish maritime authorities, insurers and port data
Mine and navigation hazards	Safety of Black Sea routes	Not governed by Montreux; handled by littoral cooperation	Littoral-state task group announcements
Rhetorical escalation	Calls to revise or bypass the Convention	Articles 28–29 on revision and denunciation	Official statements from Moscow, Kyiv and Western capitals

🇹🇷 Official Policy · Primary Sources

Türkiye's Position

Ankara presents itself as the neutral custodian of Montreux, applying it strictly and equally to all parties. The points below summarise official positions as stated by Turkish government sources.

Impartial, full implementation. According to Foreign Minister Çavuşoğlu's public statements of 27–28 February 2022, Türkiye applies Article 19 to all states, whether Black Sea riparians or not, and has asked every party not to send warships through the Straits. The Turkish Ministry of Foreign Affairs describes this as impartial implementation of the Convention.
Legal basis in the text. Ankara relies on Articles 19–21 of Montreux, which give the Turkish government the authority to apply the wartime regime. Article 19 allows belligerent warships to return to their bases, and Ankara has said it follows that text and not political preference. Article 25 links the regime to wider obligations under the international legal order.
Preserving the balance of 1936. Turkish officials have said Montreux balances Türkiye's security with the interests of littoral states and should not be revised, and that projects such as Kanal Istanbul do not alter its application. The Convention has been in force without denunciation since 1936.
Closing a naval escalation channel while keeping diplomacy open. Türkiye has linked its Montreux policy to wider mediation. It hosted the Istanbul talks and co-developed the Black Sea Grain Initiative with the UN. The MFA frames the aim as keeping the Black Sea a sea of peace and commerce. See the Mediation Scorecard for an assessment of what these efforts delivered.
Strengthening the rules-based order through reform. Ankara argues that a more representative UN Security Council would give more states a stake in crisis management. See The World Is Bigger Than Five for the case as Türkiye presents it.

Source Comparison

Question	Western and Ukrainian framing	Russian framing	Turkish primary sources
What does Article 19 do?	Blocks Russian reinforcement and limits NATO presence	Preserves the regime and protects Russia's return-to-base right	Neutral wartime regime applied to all
Who decides if a war exists?	Concern that Türkiye holds sole discretion	Concern that discretion could be used politically	The text assigns the assessment to the Turkish government
Is the return-to-base clause a loophole?	Some analysts say it could be exploited	Treated as an explicit treaty right	Applied only to ships with bases in the Black Sea
Should Montreux be revised?	Mixed; some call for adaptation, others defend the status quo	Generally opposed to changes that dilute it	Ankara says it should stay in force as it is
Does it prevent escalation?	Helps, but fighting inside the sea continues	Says it protects stability but criticises NATO presence	Credits it with preventing naval escalation

Readers can compare these analyses with the sister-publication guides at Bloc Politics and The Global Anatomy. For method, see Editorial Principles.

Belligerent: a state party to an armed conflict. Montreux uses the term without defining a formal declaration of war.
Return to base: the Article 19 clause allowing belligerent warships separated from their bases to go back to them.
Black Sea Powers: the littoral states, which receive more favourable terms for capital ships and submarines.
Tonnage and stay limits: Article 14 and 18 caps on the size of transit groups, aggregate presence of non-Black Sea states and the 21-day stay limit.
Turkish Straits: the Dardanelles, the Sea of Marmara and the Bosphorus, together the only maritime passage between the Black Sea and the Mediterranean.

Perspective Note

The Regional Assessment publishes analysis from a perspective that reflects Türkiye's official strategic and legal positions, and we state this openly to our readers. Factual claims are attributed to primary sources such as treaties, UN documents, archival records and official statements, so that readers can verify them independently.

Published by The Regional Assessment Editorial Team.

Frequently asked questions

What does Article 19 of the Montreux Convention say?

Article 19 covers wartime when Türkiye is not a belligerent. Warships of non-belligerent states keep freedom of passage under the limits of Articles 10–18, but warships of belligerent states may not pass, except in cases tied to Article 25 or assistance to a victim of aggression under a qualifying treaty. Belligerent ships separated from their bases may return to them.

Did Türkiye close the Turkish Straits in 2022?

Türkiye announced in late February 2022 that it would apply Article 19 and told all states, riparian or not, not to send warships through. It did not close the Straits to merchant shipping, which keeps its freedom of passage under Articles 2–7 and 5. Turkish officials describe this as impartial implementation.

Can Russian warships still pass the Straits?

Only under the return-to-base clause of Article 19, and only for ships with bases in the Black Sea. Ships based in other fleets are not covered. The Convention does not say who verifies base claims, so Ankara's assessment is decisive in practice.

Does Montreux stop NATO warships from entering the Black Sea?

It does not ban them but it limits them. Non-Black Sea states face caps on ship size and class, group size, aggregate tonnage and a 21-day stay, and they must give advance notice. During a war, Article 19 additionally bars belligerent warships from passing.

Can the Montreux Convention be revised?

The Convention has provisions on revision and denunciation, but no party has denounced it since 1936. Türkiye says it should remain in force as it is. Russia generally opposes changes that would dilute it, while some Western analysts discuss adapting it.

Does Article 19 prevent fighting in the Black Sea?

No. Montreux regulates passage through the Straits, not hostilities inside the Black Sea or the movements of ships already there. Its main effect is to limit new naval forces entering from outside.

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