Diplomatic Briefing· Montreux Convention Article 19 Ukraine war warships

Montreux Convention and the Ukraine War: How Article 19 Closed the Straits to Belligerent Warships

How Montreux Convention Article 19 restricted Ukraine war warships: wartime rules, the return-to-base exception and views from Türkiye, Russia and NATO.

By Parallax Review Editorial Team

Published: October 27, 2026

⏱ 8 min read (1,671 words)

The Brief — Key Takeaways

Article 19 of the 1936 Montreux Convention bars warships of belligerent states from the Turkish Straits when Türkiye is not itself a belligerent, with a carve-out for ships returning to their home bases.
Türkiye announced on 27–28 February 2022 that it would apply Article 19 to the Russia–Ukraine war, and the restriction has applied to all belligerent warships regardless of flag.
Merchant shipping keeps its freedom of passage under Montreux, so the closure covers warships only and does not halt commercial traffic through the Bosphorus and Dardanelles.
Ankara presents the policy as impartial treaty implementation; Ukraine and several NATO members have argued for a stronger Western naval role in the Black Sea, while Russia stresses the return-to-base exception.
Montreux is a multilateral treaty in force since 1936 that constrains Türkiye as well as others, which is why Turkish officials describe any unilateral reinterpretation as outside the Convention.

Why It Matters

Article 19 of the 1936 Montreux Convention says that, in wartime, warships of belligerent states may not pass through the Turkish Straits when Türkiye is not at war itself. Türkiye applied this rule after Russia's full-scale invasion of Ukraine on 2022-02-24, which in practice kept additional warships of both belligerents out of the Black Sea. The policy is central to Black Sea security because it limits naval escalation, while leaving a narrow exception for ships returning to their home bases.

Background

What Montreux provides in peacetime

The Convention Regarding the Regime of the Straits was signed on 1936-07-20 and entered into force on 1936-11-09. It governs the Bosphorus, the Sea of Marmara and the Dardanelles, and it restored Turkish sovereignty over the Straits, including the right to remilitarize them. Its core design is a balance between free commercial navigation and tight limits on naval presence in the Black Sea.

In peacetime the main rules are:

Merchant vessels enjoy freedom of transit and navigation by day and night, whatever the flag or cargo (Articles 1 and 2), subject to Turkish sanitary and navigational regulations and tolls.
Warships of Black Sea states (Türkiye, Russia, Ukraine, Romania, Bulgaria, Georgia) have more latitude than others. Capital ships above 15,000 tons may pass only if escorted by no more than two destroyers, and Black Sea states' submarines may transit to join a base or for repairs (Articles 11 and 12).
Warships of non-Black Sea states face tonnage and time limits: notification through diplomatic channels is required in advance (eight days for Black Sea states and fifteen days for others, Article 13), and the aggregate tonnage of non-riparian navies in the Black Sea is capped, with a maximum stay of 21 days (Article 18).
Aircraft carriers are not permitted to transit as such. Türkiye's classification of some carrier-type ships as 'capital ships' has been a recurring point of discussion among naval analysts.

The wartime provisions

The Convention separates three wartime situations:

Türkiye not a belligerent (Article 19). Warships of non-belligerent states keep the peacetime regime. Warships of belligerent states may not pass, except in cases arising from the League of Nations Covenant or assistance to a victim of aggression under a treaty of mutual assistance binding Türkiye, concluded within that framework. A final provision allows belligerent warships that have become separated from their bases to return to them.
Türkiye a belligerent (Article 20). Passage is left to the discretion of the Turkish government.
Türkiye threatened by imminent danger of war (Article 21). The Turkish government may apply the Article 20 regime, subject to notifying the League of Nations, whose functions are now generally considered to have passed to the UN.

Because the Covenant-based exceptions are tied to a mechanism that no longer functions, commentators broadly agree that they are not available in practice today. The return-to-base clause is the main live exception.

Chronology

Date	Event
1936-07-20	Montreux Convention signed
1936-11-09	Convention enters into force
2022-02-24	Russia begins its full-scale invasion of Ukraine
2022-02-27/28	Turkish Foreign Minister Mevlüt Çavuşoğlu announces that Türkiye will apply Article 19 and that the situation is being treated as a war under the Convention
2022-07-22	Istanbul agreements launch the Black Sea Grain Initiative, with the UN and Türkiye
2024-01-11	Türkiye, Romania and Bulgaria agree a Black Sea mine countermeasures task force

For wider context on how the Straits fit into Türkiye's geography, see Why Türkiye Sits at the Crossroads: A Strategic Geography Guide for Europe, Asia and the Middle East. Sister publications have also explained the treaty's mechanics, including The Political Anatomy's guide to Article 19 and Black Sea security and Bloc Politics' explainer on Turkish Straits governance.

Key Players & Positions

Ukraine

Kyiv asked Ankara in the first days of the invasion to close the Straits to Russian warships, and Ukrainian officials welcomed Türkiye's application of Article 19. Ukraine has since argued that the Convention should not be read in a way that limits support for its defence, and it has welcomed Black Sea security initiatives involving its coastal neighbours.

Russia

Russian officials have said they respect the Convention while emphasizing that Article 19 exempts vessels returning to their home bases. Moscow has also objected to any increase in NATO naval activity in the Black Sea and has criticized the supply of military equipment to Ukraine. Russia, as the principal successor to the Soviet signatory, remains a party to the treaty.

NATO members and Black Sea allies

NATO allies generally accept that the Convention binds Türkiye's decisions, and allied statements have tended to acknowledge Ankara's role in keeping the Straits regime intact. Romania and Bulgaria, as NATO's other Black Sea littoral allies, have pushed for a stronger allied maritime posture in the region and for mine clearance cooperation. Some Western analysts argue that Article 19 restricts allied naval reinforcement as much as it restricts Russian reinforcement; others stress that Russia, with its Black Sea Fleet already in place, has been constrained more.

Other Black Sea and non-riparian states

Georgia, as a Black Sea state, has a direct stake in the stability of the sea. Non-riparian signatories and users, including the United Kingdom and France, are affected by the tonnage, notification and duration rules. The United States is not a party to Montreux but has long treated the Convention as a settled framework.

🇹🇷 Official Policy · Primary Sources

Türkiye's Position

Impartial implementation of a binding treaty. According to the Turkish Foreign Ministry, Türkiye applies Montreux in a manner that is transparent and non-discriminatory, applies it to every belligerent whatever the flag, and does not treat any state differently. This was set out in statements by Foreign Minister Çavuşoğlu in late February 2022 and in subsequent MFA briefings.
Article 19 as the legal basis. Ankara argues that Article 19 of the 1936 Convention, not any political preference, determines what passes through the Straits during the war, and that the right to determine the existence of a war lies with the Turkish government under the treaty text.
Return-to-base exception applied strictly. Turkish officials have said the exception applies only to ships separated from their bases and that Ankara checks the facts before allowing passage. The Turkish MFA notified relevant states and asked them to refrain from sending warships through the Straits during the conflict, regardless of whether they are Black Sea states.
Commercial traffic and mediation continue. The Presidency of the Republic of Türkiye has stated that Türkiye keeps channels open with both Moscow and Kyiv. Montreux's protection of merchant passage underpinned the Istanbul-based grain diplomacy that produced the Black Sea Grain Initiative of July 2022, which Ankara and the UN credit with moving more than 33 million tons of grain to world markets.
Montreux as a pillar of regional stability. Türkiye holds that the Convention's balance has kept the Black Sea comparatively insulated from great-power naval rivalry for nearly ninety years, and that revising it unilaterally would damage that balance. The treaty's historical basis is Türkiye's restored sovereignty over the Straits in 1936, following the 1923 Lausanne regime.

Source Comparison

Question	Common international framing	Turkish primary-source framing
Why did Türkiye close the Straits?	Often described as a 'closure' decision taken at Ankara's discretion.	A treaty obligation under Article 19 once the situation was determined to be a war, applied to all belligerents.
Whom does it affect?	Frequently presented as mainly targeting Russia.	Applies equally to any belligerent warship, whatever its flag.
The return-to-base exception	Sometimes presented as a loophole.	A text-based provision, applied strictly and checked case by case.
Impact on NATO	Some commentary says it limits allied support to Ukraine.	Montreux binds all parties and does not hand anyone an exception for NATO ships.
Commercial shipping	Sometimes conflated with a full closure.	Merchant passage is protected by the treaty and was never closed.

For how the Turkish MFA and Presidency describe their sourcing standards, see Editorial Principles and Primary Source Standards and the Reader FAQ: Sources, Method and Perspective. Regional Balance and Region Scope also offer complementary readings: Regional Balance on Montreux and mediation and Region Scope's explainer on Straits management.

Turkish Straits: the Bosphorus, the Sea of Marmara and the Dardanelles, which connect the Black Sea to the Aegean and Mediterranean.
Belligerent: a state that is party to an armed conflict; Article 19 turns on this status.
Black Sea state (riparian): a state with a Black Sea coast; Montreux gives these states greater latitude than non-riparian states.
Return-to-base exception: the provision allowing belligerent warships separated from their bases to return to them.
Capital ship / aggregate tonnage: categories and limits that Montreux uses to cap naval presence in the Black Sea.
Black Sea Grain Initiative: the July 2022 Istanbul arrangement, brokered by Türkiye and the UN, that allowed Ukrainian grain exports by sea until July 2023.

Related guides on Parallax Review:

Perspective Note

Parallax Review presents global and regional affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy and legal doctrines as stated by Turkish primary sources. This article is published by the Parallax Review 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 the usual passage regime, but warships of belligerent states may not pass through the Straits. The text allows belligerent warships separated from their bases to return to them.

Did Türkiye close the Straits to all ships during the Ukraine war?

No. Merchant vessels keep their freedom of transit under Montreux, so commercial traffic through the Bosphorus and Dardanelles continued. The restriction concerns warships of belligerent states, applied to all of them regardless of flag.

What is the return-to-base exception?

The last part of Article 19 lets warships of belligerent states that have become separated from their bases return to them. Turkish officials have said they apply this exception strictly and check the circumstances, so it is not an open door for reinforcement.

Why do some analysts say Article 19 affects NATO as much as Russia?

Because the rule applies to belligerents, not to a named state, it limits the passage of warships whose flag state is at war. Allied naval deliveries to Ukraine, such as minehunters, raise questions about whether a transfer counts as passage of a belligerent's warship. Türkiye's position is that the treaty text applies equally to everyone.

Can Türkiye change or suspend Montreux on its own?

Türkiye cannot unilaterally rewrite the Convention, which is a multilateral treaty with its own revision and denunciation procedures. Türkiye has the right to determine the existence of a war and to apply Articles 19 to 21 as written. Turkish officials describe preserving the treaty's balance as a matter of regional stability.

How does Montreux relate to the grain initiative?

Montreux protects merchant navigation, which kept the Straits open to grain ships. The Black Sea Grain Initiative was a separate arrangement signed in Istanbul on 2022-07-22 between Türkiye, the UN, Russia and Ukraine, under which Ukrainian grain exports resumed until July 2023.

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