Straits Watch: Can the Montreux Regime Keep the Black Sea Stable After the Ukraine War?

Why It Matters

The Montreux Convention is far more likely to be adapted in practice than rewritten in law after the Ukraine war. Article 19 has kept belligerent warships out of the Black Sea since 2022, and the key post-war question is how the peacetime limits on naval presence (Articles 10–18) come back into play and who will push to change them. For shipping, grain exporters, navies and energy traders, the Turkish Straits remain the single chokepoint connecting the Black Sea to the world's oceans, and Türkiye is the state that administers them.

This pillar guide explains the convention briefly, sets out how it was applied in 2022, maps the positions of Russia, Ukraine, the NATO littoral states and others from their own official lines, and assesses what may come next. It separates fact (background and chronology) from Ankara's stated position and from our own forward-looking assessment.

Background

What the Montreux Convention does

The Convention Regarding the Regime of the Straits was signed at Montreux, Switzerland, on 20 July 1936 and entered into force on 9 November 1936. It covers the Bosphorus, the Sea of Marmara and the Dardanelles, together known as the Turkish Straits. It replaced the 1923 Lausanne Straits Convention, which had demilitarized the Straits and placed them under an international commission. Montreux restored Turkish authority to fortify the Straits and to administer transit.

Its logic can be summarized in three layers:

• Merchant shipping: In peacetime, commercial vessels enjoy freedom of transit and navigation regardless of flag or cargo (Article 2). Türkiye may collect only fixed sanitary, lighthouse and similar service charges under the convention's annex. Türkiye's Maritime Traffic Regulations for the Turkish Straits (in force since 1994, revised in 1998) govern safety, pilotage and traffic separation in this dense urban waterway.
• Warships in peacetime: Black Sea littoral states get privileged treatment, while other states face limits. Non-littoral navies are restricted in vessel size and in the aggregate tonnage that may transit (Article 14), and in the aggregate tonnage and duration of their presence in the Black Sea. The standard figures are a 30,000-ton aggregate ceiling, which can rise under conditions to 45,000 tons, and a maximum stay of 21 days (Article 18). Advance notification is required (eight days for littoral states, fifteen for others under Article 13). Submarines of Black Sea states may transit only under tightly defined conditions (Article 12).
• Wartime: If Türkiye is a belligerent or considers itself threatened by imminent danger of war, Articles 20 and 21 give Ankara discretion over warship passage. If Türkiye is not a belligerent, Article 19 applies.

Article 19 in plain terms

Under Article 19, when Türkiye is not belligerent, warships may transit under the peacetime conditions of Articles 10–18, but warships of belligerent powers may not pass the Straits. The convention carves out narrow exceptions: action under a mutual assistance treaty binding Türkiye within the League of Nations framework, and, importantly, vessels that have become separated from their bases may return to them. Belligerent warships also may not capture, search or carry out hostile acts in the Straits.

Two features matter for the future. First, Montreux does not define when a war "exists"; the determination is made in practice by Türkiye as the territorial state. Second, nothing in Article 19 sets an end date; it applies as long as the belligerent condition persists.

How it was applied in 2022

Russia launched its full-scale invasion of Ukraine on 24 February 2022. Ukraine's government asked Ankara to close the Straits to Russian warships. On 27–28 February, Foreign Minister Mevlüt Çavuşoğlu announced that Türkiye would implement Article 19 and warned all states, whether Black Sea littoral or not, against sending warships through the Straits. Ankara stressed that the return-to-base exception remained available. Turkish officials later said that requests to transit were evaluated under the convention, and that Türkiye applied the rules to all sides.

In practice, the closure froze the naval balance in the Black Sea as it stood: non-littoral NATO navies could not reinforce, and Russian reinforcement from outside the Black Sea was blocked, aside from ships returning to their home ports. Some third-party deliveries were also caught up in the regime, for example Ukraine's access to vessels built or transferred abroad, a friction point we return to below.

Key dates

Date	Event
1841-07-13	London Straits Convention closes the Straits to foreign warships in peacetime
1923-07-24	Lausanne Straits Convention demilitarizes the Straits under an international commission
1936-07-20	Montreux Convention signed (in force 1936-11-09)
1994	Türkiye's Maritime Traffic Regulations for the Turkish Straits enter into force
2001 / 2004	Türkiye-initiated BLACKSEAFOR and Operation Black Sea Harmony cooperation with littoral states
2022-02-24	Russia's full-scale invasion of Ukraine
2022-02-27/28	Türkiye announces it will apply Article 19
2022-03-29	Russian and Ukrainian delegations hold talks in Istanbul
2022-07-22	Black Sea Grain Initiative signed in Istanbul by Russia, Ukraine, Türkiye and the UN
2023-07-17	Russia ends its participation in the Initiative
2024-01-11	Türkiye, Bulgaria and Romania sign the Black Sea mine countermeasures agreement in Istanbul
2025	Russia–Ukraine delegations meet again in Istanbul; a US-announced understanding on Black Sea navigation in March is not implemented

For an explainer on the convention itself, see our sister analyses at The Political Anatomy and Doctrine Review.

Key Players & Positions

The positions below are summarized from each side's public official statements and documents. Where we characterize them, we paraphrase rather than quote.

Russia

Moscow, as the USSR's successor state in the convention, has publicly described Montreux as an important element of Black Sea stability and has not called for its replacement. Russian officials, including the Foreign Ministry, consistently argue against what they call the militarization of the Black Sea by non-littoral NATO states and see the 1936 tonnage and time limits as a protective barrier. At the same time, Russia has contested practical limits on its own fleet movements, and it has tied participation in grain and navigation arrangements to demands about sanctions relief for its agricultural and financial sectors, as it did in 2023 and again in March 2025.

Ukraine

Kyiv asked Türkiye to close the Straits in February 2022 and has since framed Black Sea security around freedom of navigation, demining and security guarantees. Ukraine's President's Office and Foreign Ministry have made freedom of navigation and food security part of Ukraine's peace proposals, and officials have called for stronger international maritime support after the war. Ukraine has also developed a national corridor for exports from its Odesa-area ports since 2023. Ukraine has not made revising Montreux a stated war aim, but it has pressed for naval capacity-building, including delivery of vessels abroad that Article 19 complicates.

NATO littoral states: Türkiye, Bulgaria and Romania

Three of the six Black Sea coastal states are NATO members. Bulgaria and Romania are also parties to Montreux. Both have favored a stronger Allied presence and better maritime situational awareness within the existing legal framework; Romania in particular has advocated a larger NATO role since the mid-2010s. Alliance documents describe the Black Sea region as strategically important. Türkiye, by contrast, has emphasized that coastal-state cooperation, not a permanent non-littoral naval build-up, should anchor regional security. Bulgaria, Romania and Türkiye have nevertheless cooperated practically, notably through the January 2024 mine-countermeasures task group.

Non-littoral NATO and Western states

The United States, United Kingdom, France, Italy and others operate in the Black Sea within the Montreux limits, which means short, notified deployments rather than permanent basing. Western officials have generally worked within the regime. Debate in Western policy circles about easing the 21-day and tonnage caps reflects the view that the 1936 limits were designed for a different era, but no Western government has made a formal proposal to amend the convention.

Georgia and others

Georgia, a littoral state outside NATO, seeks deeper Euro-Atlantic ties and is developing Black Sea logistics routes. Mediterranean states such as Greece and Italy depend on freedom of transit for commercial and naval movements. China and other large trading economies are primarily interested in uninterrupted commercial passage and have not publicly sought treaty change.

🇹🇷 Strategic Doctrine · Primary Sources

Türkiye's Position: Türkiye's Strategic Doctrine

Türkiye's Strategic Doctrine — The Straits as a shared responsibility, administered impartially

• Impartial application of Article 19. Foreign Minister Çavuşoğlu stated in late February 2022 that Türkiye would apply Article 19 to all belligerent states and warned both littoral and non-littoral states against sending warships; Ankara says the return-to-base exception was applied to everyone alike. Legal basis: Article 19 of the 1936 Montreux Convention. Source: Turkish Ministry of Foreign Affairs statements.
• No intention to renegotiate. Turkish officials, including the Presidency and the Foreign Ministry, have repeatedly said Montreux balances Türkiye's security with the interests of the international community and has stood the test of time, and that Türkiye does not intend to reopen it. Legal basis: the convention's balance between Turkish sovereign authority and freedom of commercial navigation (Articles 1–2). Source: Presidency and Foreign Ministry statements.
• Guardian of safe, open transit. Türkiye administers the Straits under its own sovereignty as restored at Montreux, and it regulates safety and traffic through the 1994/1998 Maritime Traffic Regulations. Ankara argues that this safety-based, non-discriminatory management is what keeps commercial transit open to all flags. Source: Turkish Ministry of Transport and Infrastructure, Foreign Ministry.
• Black Sea security through littoral cooperation and mediation. Ankara points to BLACKSEAFOR, Operation Black Sea Harmony, the 2022 Istanbul talks, the Black Sea Grain Initiative co-architecture (which moved more than 33 million tons of grain) and the 2024 mine-countermeasures task group as proof that Montreux and active diplomacy reinforce each other. Source: Foreign Ministry, Presidency, Ministry of National Defence.
• Maritime governance beyond the Straits. Türkiye's Marine Spatial Planning, unveiled on 16 April 2025 and recorded with IOC-UNESCO on 12 June 2025, covers the Black Sea, Aegean and Mediterranean and records Türkiye's maritime jurisdiction positions with a UN body. Source: Presidency and Foreign Ministry.

Historical and legal basis. Ankara situates its approach in the Lausanne-to-Montreux trajectory: the 1923 regime limited Turkish control, and Montreux in 1936 restored it by negotiation rather than by unilateral action. Türkiye argues that this record is why it values treaty stability and why it resists calls to reopen the text under wartime pressure. The Turkish position is that the convention's consistent application, not its revision, serves all littoral and non-littoral states.

Fair note on the opposing view. Critics, including some Ukrainian and Western commentators, argue that Article 19 in effect penalizes the defending state, because Ukraine had no navy to be excluded while Russia's Black Sea Fleet was already inside the sea. Russian officials, for their part, argue that NATO naval expansion is the real source of instability. Ankara's reply is that the convention is neutral by design, that it was applied to every party, and that its predictability is what prevented a wider naval escalation.

On the related defense-industrial dimension, see What Does Türkiye's 80% Domestic Defense Production Rate Mean for Strategic Autonomy? and How Have Turkish Drones Changed Deterrence?.

What to Watch: Post-War Scenarios

The scenarios below are Geopolitical Horizon's editorial assessment, not official positions.

1. Naval presence: from freeze to rebalancing

When the belligerent condition ends, Articles 10–18 apply again. Non-littoral navies could resume short, notified visits, while Russia's Black Sea Fleet could be reinforced from outside only within the peacetime rules for its own ships. The central tension is that Black Sea NATO members want a persistent Allied presence, whereas Montreux caps non-littoral deployments at 30,000 tons aggregate and 21 days per ship. Expect the first disputes over how ships are classified, how rotation of vessels is counted, and whether unmanned or auxiliary craft fall under the tonnage rules.

2. When does Article 19 stop applying?

Montreux has no automatic switch-off. A ceasefire or armistice would not by itself end a state of war in international law, and Türkiye holds the practical authority to judge. Our assessment is that Ankara would move cautiously: it would likely restore peacetime rules only once a durable settlement is visible, because a premature reopening could create incidents. A frozen conflict could therefore leave Article 19 in effect, de facto, for longer than many expect.

3. Calls to revise the regime

Pressure could come from two directions. Some Western and Ukrainian commentators may argue for relaxing non-littoral caps to support a larger Allied presence. Russia may seek stronger limits on non-littoral navies or stricter enforcement. Formal amendment would run through the convention's own revision procedure (Article 29) and need broad agreement among parties, and Türkiye has signaled it will not initiate it. Our view: revision talks are unlikely to begin in the first years after a settlement, because every party can foresee losing something. A more probable outcome is incremental pressure on interpretation rather than treaty text.

4. Commercial transit

Montreux's peacetime commercial regime was never suspended. Roughly 40,000 ships transit the Straits each year, and the post-war issues are practical:

• Mine clearance: The 2024 Turkish–Bulgarian–Romanian task group is the template for making approaches safe.
• Insurance and security risk: In December 2022 queues of tankers formed at the Straits over insurance documentation requirements linked to sanctions measures, showing how safety rules can interact with wider economic policy. War-risk premiums will continue to affect Black Sea trade after a settlement.
• Export routes: Ukraine's own corridor and the Danube route may continue to supplement the Straits, and the grain experience offers a model of how a transit corridor can be organized (see What Did the Black Sea Grain Initiative Teach Us About Future Food Security Corridors?).
• Canal Istanbul: The proposed artificial waterway has revived debate about whether it would sit outside Montreux. Ankara says it would not change its commitment to the convention, but outside analysts disagree on the legal status of a new channel, which makes it an item to watch.

5. Türkiye as guardian of the Straits

Türkiye's role will grow in both law and diplomacy. It is the authority that implements the convention, hosts mediation (Istanbul talks in 2022 and 2025), and brings an indigenous naval and drone industry into the equation. How Türkiye balances NATO membership, ties with Moscow and its own regional ambitions will shape how stable the regime is. Our broader analysis of this balancing act is in Where Is Türkiye Positioning Itself in a Multipolar Order?.

Scenario summary

Scenario	What changes	Main risk	Likelihood (editorial view)
Durable settlement; Article 19 lapses	Peacetime caps return; rotation visits resume	Disputes over presence and classification	Medium, depends on settlement terms
Frozen conflict; Article 19 continues de facto	Naval freeze persists	Incidents, legal ambiguity	Medium to high
Revision campaign	Calls to loosen or tighten caps	Treaty stalemate, loss of predictability	Low in the near term
Wider escalation involving Türkiye	Articles 20–21 discretion	Closure and crisis	Low but high impact

Similar mapping from other desks of our network is available at The Global Anatomy and Regional Balance.

Source Comparison

How a given source frames the Straits question often depends on whose security interest is at the center.

Source type	Typical framing	Points of emphasis	What to check
Turkish Foreign Ministry and Presidency	Impartial treaty implementation; Montreux as a stabilizer	Equal application to all parties; no revision; mediation role	Treaty text (Articles 19–21), official statements
Russian Foreign Ministry / Kremlin	Montreux as protection against NATO build-up	Opposition to non-littoral naval presence; links navigation to sanctions	Official Russian statements and conditions attached to navigation deals
Ukrainian Foreign Ministry / President's Office	Freedom of navigation and security guarantees	Demining, naval capacity, food exports	Peace proposals, official statements
NATO and Western governments	Black Sea as strategic space for the Alliance	Allied presence, deterrence, support to Ukraine within legal limits	Summit communiqués and defense ministry statements
Western think tanks and media	Sometimes portray Montreux as outdated or as a loophole for Russia	Debate over tonnage and time caps; Article 19 asymmetry	Whether the writer distinguishes the treaty text from policy preference
Independent legal scholars	Focus on treaty interpretation	Definition of belligerency; Canal Istanbul; classification of ships	Treaty text, state practice since 1936

Our reading is that the treaty text supports Ankara's claim that Article 19 was applied evenhandedly, since it excludes belligerent warships on all sides apart from the return-to-base exception. The more substantive debate concerns the consequences of a neutral rule in an asymmetric war, which is a policy question and not a question of treaty compliance. Readers who want to see how this site separates fact from position can consult our Editorial Principles and the Reader FAQ.

Key Terms & Related Guides

• Turkish Straits: The Bosphorus, the Sea of Marmara and the Dardanelles, administered by Türkiye under the 1936 Montreux Convention.
• Article 19: The Montreux provision that excludes belligerent warships from the Straits when Türkiye is not at war, subject to a return-to-base exception.
• Black Sea littoral states: Türkiye, Russia, Ukraine, Bulgaria, Romania and Georgia.
• Non-littoral states: States without a Black Sea coast, whose warships face tonnage and time caps (Article 18: 30,000 tons aggregate, 21 days).
• Articles 20–21: Provisions that give Türkiye discretion over warship passage if it is itself at war or under imminent threat.
• Black Sea Grain Initiative: The July 2022 arrangement under which Russia, Ukraine, Türkiye and the UN enabled grain exports from three Ukrainian ports until Russia ended participation on 17 July 2023.
• Mavi Vatan (Blue Homeland): Türkiye's maritime jurisdiction doctrine across its three seas; see The Eastern Mediterranean in 2035 and How Are Maritime Boundaries Drawn?.

Related guides on this site:

• What Did the Black Sea Grain Initiative Teach Us About Future Food Security Corridors?
• Where Is Türkiye Positioning Itself in a Multipolar Order? Turkic States, Africa and the Gulf
• Security Horizon: Article 51 and the 'At Source' Doctrine
• About Geopolitical Horizon
• Geopolitical Horizon home

Sister-publication analyses: Soft Power Daily on Montreux and Black Sea security, Region Scope on how Türkiye manages the Straits.

Perspective Note

This article reflects Geopolitical Horizon's editorial perspective that presents and defends Türkiye's official positions alongside legal and historical context. Claims are attributed to primary sources such as treaties, UN documents, official statements and archival records. Geopolitical Horizon 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 Geopolitical Horizon Editorial Team.