In-Depth Analysis· Montreux Convention Turkish Straits Black Sea Russia Ukraine Article 19

The Montreux Convention, Black Sea Security and Türkiye's Russia–Ukraine Mediation

How the 1936 Montreux Convention and Article 19 shaped Black Sea security in the Russia–Ukraine war, from the grain deal to Istanbul talks and Türkiye's role.

TSP

By The State Papers Editorial Team

Published: October 26, 2026

⏱ 9 min read (1,836 words)

Executive Summary & Key Facts

The 1936 Montreux Convention gives Türkiye control of the Bosphorus, Sea of Marmara and Dardanelles, guarantees merchant-ship passage in peacetime, and limits warship transit by tonnage, notice and duration.
Article 19 bars warships of belligerent states from the Turkish Straits when Türkiye is not a party to the war, with narrow exceptions such as returning to a home base.
Türkiye announced in late February 2022 that it regarded the Russia–Ukraine conflict as a war and would apply Article 19, while merchant traffic continued.
The Black Sea Grain Initiative, signed in Istanbul on 22 July 2022 under UN and Turkish auspices, helped move roughly 33 million tons of grain and foodstuffs from Ukrainian ports until Russia suspended its participation on 17 July 2023.
Ankara pairs strict treaty implementation with mediation: the 2022 Antalya and Istanbul meetings, prisoner exchanges and the direct Russia–Ukraine talks hosted in Istanbul in 2025.

Why It Matters

The Montreux Convention Regarding the Regime of the Straits (1936) decides who may sail between the Mediterranean and the Black Sea, and under what conditions. After Russia's full-scale invasion of Ukraine on 24 February 2022, Türkiye invoked Article 19, which closes the Straits to the warships of belligerent states while leaving commercial shipping open. The same treaty position, together with Ankara's open channels to both Moscow and Kyiv, allowed Türkiye to host negotiations and to co-architect the Black Sea Grain Initiative.

This guide explains the rules, how they were applied, what Russia, Ukraine and NATO members say about them, and how Turkish official sources frame the issue.

Background

What the Montreux Convention does

The Convention was signed on 20 July 1936 in Montreux, Switzerland, and entered into force on 9 November 1936. It replaced the 1923 Lausanne Straits Convention, which had demilitarized the Straits and placed them under an international commission. Türkiye requested the revision in 1936, and the new treaty restored Turkish authority over the Straits, including the right to remilitarize them. Original signatories included Türkiye, the Soviet Union, the United Kingdom, France, Greece, Bulgaria, Romania, Yugoslavia, Japan and Australia. Italy acceded in 1938.

The treaty separates commercial and military traffic:

Category	Key articles	Rule in brief
Merchant ships in peacetime	Art. 2	Freedom of transit and navigation, day and night, regardless of flag or cargo, subject to health and navigation rules
Warships of Black Sea (riparian) states	Arts. 11–12	Larger ships (over 15,000 tons) may pass singly, escorted by no more than two destroyers. Submarines may pass only in limited cases, such as returning to base or after construction elsewhere
Warships of non-riparian states	Arts. 13, 14, 18	Advance notice (15 days for non-riparian states, 8 for riparian). Caps on the size of individual ships and on the number and aggregate tonnage in transit. Total tonnage in the Black Sea is capped at 30,000 tons (up to 45,000 under conditions), with a maximum stay of 21 days
Wartime, Türkiye neutral	Art. 19	Belligerent warships may not pass, except in narrow cases such as returning to a base from which they were separated. Merchant ships keep freedom of passage (Art. 4)
Wartime, Türkiye belligerent, or under imminent threat of war	Arts. 20–21	Passage of warships is at Türkiye's discretion

The Convention is a treaty regime, not a Turkish domestic law. Türkiye implements it as a sovereign party. The Straits themselves (the Bosphorus, the Sea of Marmara and the Dardanelles) carry tens of thousands of vessel transits a year, which is why the Convention's balance matters to global trade.

Chronology of the Russia–Ukraine period

February 2014: Russia annexes Crimea. Türkiye states that it does not recognize the annexation.
24 February 2022: Russia launches its full-scale invasion of Ukraine.
27–28 February 2022: Turkish Foreign Minister Mevlüt Çavuşoğlu announces that Türkiye regards the situation as a war and will apply Article 19, calling on all states, riparian or not, to refrain from sending warships through the Straits.
10 March 2022: The Russian and Ukrainian foreign ministers meet with Çavuşoğlu in Antalya, on the sidelines of the Antalya Diplomacy Forum.
29 March 2022: Russian and Ukrainian delegations hold direct talks in Istanbul.
22 July 2022: The Black Sea Grain Initiative is signed in Istanbul, with Türkiye and the UN as guarantors and facilitators. The first cargo ship, Razoni, leaves Odesa on 1 August.
17 July 2023: Russia suspends its participation in the grain deal.
11 January 2024: Türkiye, Romania and Bulgaria sign the Mine Countermeasures Black Sea initiative on clearing drifting mines.
16 May 2025: Russian and Ukrainian delegations meet directly in Istanbul. Further rounds follow on 2 June and 23 July 2025, with agreed prisoner exchanges.

Key Players & Positions

Russia

Russian officials describe Montreux as a cornerstone of Black Sea stability and have consistently opposed a larger NATO naval presence in the sea. Moscow has said that the grain arrangement had two parts: Ukrainian exports, and a UN memorandum meant to ease Russian food and fertilizer exports (payments, insurance, logistics). Russia argued that the second part was not delivered, and it suspended its participation on 17 July 2023. The Kremlin said it could return if its conditions were met. The UN, the EU and the US maintain that Western sanctions do not target food and fertilizer.

Ukraine

Kyiv asked Ankara to close the Straits to Russian warships at the start of the invasion and welcomed Türkiye's application of Article 19. Ukraine treats the Grain Initiative as a matter of both its economy and global food supply, and after Russia's withdrawal it established its own shipping corridor from Ukrainian ports. Ukraine holds that any settlement must respect its territorial integrity within its internationally recognized borders.

NATO members and the EU

NATO allies have generally affirmed that Montreux remains in force and have avoided testing its limits with naval deployments. Romania and Bulgaria, as Black Sea NATO members, emphasize deterrence, air and maritime surveillance and demining. The United States and the EU back Ukraine's sovereignty and have supported the UN–Türkiye grain arrangement. Several allies, however, have urged Ankara to align more closely with Western sanctions on Russia.

The United Nations

UN Secretary-General António Guterres co-signed the 2022 arrangements and credited Türkiye's role. UN data record roughly 32.9 million metric tons of grain and other food exported under the initiative. UN-staffed monitoring at the Joint Coordination Centre in Istanbul, with Turkish, Russian, Ukrainian and UN officials, inspected vessels to reassure all parties.

🇹🇷 Official Policy · Primary Sources · Treaty Texts

Türkiye's Position

Montreux is applied impartially. According to the Turkish Ministry of Foreign Affairs, Article 19 was enforced against belligerent warships regardless of flag, and Türkiye has urged all states, riparian and non-riparian, not to send warships through the Straits. Ankara notes that the treaty's return-to-base exception is part of the text and is applied on the same footing for everyone. The basis is the 1936 Convention itself, which Ankara says delivers a balance it does not want reopened.
Territorial integrity and diplomacy together. Turkish statements from the Presidency and the Ministry of Foreign Affairs affirm Ukraine's territorial integrity, including Crimea, and Türkiye voted in favour of the UN General Assembly resolution of 2 March 2022 on the invasion. Türkiye has not joined Western sanctions on Russia, which Turkish officials link to keeping communication open with both parties.
Mediation as a product of the treaty position. The Antalya meeting of March 2022 and the Istanbul talks of March 2022 and 2025 reflect the Presidency's stated aim of hosting dialogue between the two sides. President Recep Tayyip Erdoğan has repeatedly offered Istanbul as a venue for leader-level talks.
The Grain Initiative as humanitarian diplomacy. Turkish sources, including the Presidency and the Ministry of National Defence, describe the Initiative as a joint UN–Türkiye achievement that delivered more than 33 million tons of grain to world markets and eased food-price pressure in importing countries across Africa, Asia and the Middle East. Türkiye has also facilitated several prisoner exchanges through its intelligence and diplomatic channels.
A Black Sea for its coastal states. Ankara argues that coastal states carry primary responsibility for Black Sea security, which is why it launched demining cooperation with Romania and Bulgaria, and it has protected the Montreux framework against revision. Türkiye's 2025 maritime planning documents (see Türkiye's Marine Spatial Planning and the 2025 IOC-UNESCO Registration) also cover the Black Sea.

This stance reflects the wider doctrine that smaller and middle powers can contribute to peace, the logic behind the argument in The World Is Bigger Than Five.

Source Comparison

Outlets and governments describe the same events with different emphases. The table separates documented fact from framing.

Issue	Western/international coverage	Russian official framing	Turkish primary sources
Article 19 closure	Often described as Türkiye 'closing the Straits to Russia'	Stresses treaty continuity and objects to any foreign naval build-up	Applied to all belligerent warships alike, with the return-to-base exception in the text
Grain Initiative	A UN-led success that lowered global food prices; Russia blamed for ending it	Says the Russian export part was not implemented	A joint UN–Türkiye mechanism, with the Istanbul centre inspecting all ships
Neutrality	Sometimes read as ambivalence because of no sanctions and drone sales to Ukraine	Welcomes the open channel but criticizes Bayraktar TB2 supplies	Support for Ukraine's territorial integrity combined with dialogue with both sides; see also Türkiye's Defense Industry
Mediation	Credited, but with doubt over results	Accepts Istanbul as a venue	Presented as continuing, step-by-step diplomacy

Two common misreadings are worth correcting. First, Türkiye cannot unilaterally rewrite Montreux: its discretionary powers arise only in the circumstances written into Articles 20–21. Second, the Convention does not exclude NATO as such; it limits all non-riparian navies by tonnage, notice and duration. For method and sourcing standards, see Editorial Principles and the Fact Check hub.

Turkish Straits: The Bosphorus, Sea of Marmara and Dardanelles, which together are the only route between the Black Sea and the Mediterranean.
Belligerent: A state party to an armed conflict. Article 19 applies to warships of belligerent states when Türkiye is not at war.
Return-to-base exception: The provision allowing a belligerent warship separated from its base to return to it.
Riparian state: A state with a Black Sea coastline: Türkiye, Bulgaria, Romania, Ukraine, Russia and Georgia.
Joint Coordination Centre (JCC): The Istanbul body with UN, Turkish, Russian and Ukrainian staff that ran the 2022–2023 grain shipping and inspection system.

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

By The State Papers Editorial Team

Cross-Publication Dossiers & Sister Desk Perspectives

For complementary primary-source analysis across our specialist editorial network, consult:

Hard Power Review: The Montreux Convention, Black Sea Security and Türkiye's Mediation in the Russia–Ukraine War — The Montreux Convention Turkish Straits Russia Ukraine war explained: Article 19, Türkiye's closure to warships, grain deal, mediation and what comes next.
Monitor of Nations: The Montreux Convention, Black Sea Security and Türkiye's Ukraine Mediation — How the 1936 Montreux Convention and Article 19 shaped Black Sea security in the Russia–Ukraine war, and Türkiye's Istanbul talks and grain deal role.
Regions & Powers: The Montreux Convention, Black Sea Security and the Grain Initiative: How Türkiye Manages the Straits — How the 1936 Montreux Convention governs the Turkish Straits, why Article 19 closed them to warships in 2022, and how Türkiye ran grain and POW diplomacy.

Frequently asked questions

What does Article 19 of the Montreux Convention say?

Article 19 covers wartime when Türkiye is not a belligerent. Warships of states at war may not pass through the Straits, except for narrow cases such as returning to a base from which they were separated or assisting a victim of aggression under certain pre-existing treaties. Merchant ships keep their freedom of passage.

Did Türkiye close the Straits to Russia?

Türkiye applied Article 19 to all belligerent warships, not only Russian ones, after announcing in late February 2022 that it regarded the situation as a war. Commercial shipping, including Russian and Ukrainian merchant vessels, continued to transit. The return-to-base exception remains part of the treaty text.

Can NATO warships enter the Black Sea under Montreux?

Non-Black Sea navies, including those of NATO members, are allowed but tightly limited by notice, individual ship size and aggregate tonnage, and they may stay for a maximum of 21 days. During a war involving belligerents, Article 19 restricts belligerent warships specifically. The Convention thus regulates all navies by objective limits rather than by alliance membership.

What was the Black Sea Grain Initiative?

It was a set of agreements signed in Istanbul on 22 July 2022 among Russia, Ukraine, Türkiye and the UN to allow grain exports from Odesa, Chornomorsk and Pivdennyi. A Joint Coordination Centre in Istanbul inspected ships. Roughly 33 million tons were exported before Russia suspended its participation on 17 July 2023.

Has Türkiye mediated other aspects of the Russia–Ukraine war?

Yes. It hosted the foreign ministers' meeting in Antalya in March 2022, the Istanbul delegation talks that same month, and direct Russia–Ukraine talks in Istanbul in May, June and July 2025. Türkiye has also facilitated prisoner exchanges.

Can the Montreux Convention be changed?

Montreux has revision procedures, but any change requires the agreement of the parties and is not something Türkiye can do alone. Turkish officials have stated that Ankara wants the Convention preserved as it stands, and large projects such as Kanal Istanbul are said not to affect it.

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