Montreux Article 19 in Practice: How Türkiye Closed the Straits to Belligerent Warships and What Changed in the Black Sea

Why It Matters

Article 19 of the 1936 Montreux Convention prohibits warships of belligerent powers from passing through the Turkish Straits in wartime when Türkiye is not a belligerent. It contains a narrow exception for ships that have become separated from their bases and are returning to them. Türkiye invoked the article in late February 2022 after Russia’s full-scale invasion of Ukraine and applied it to all belligerents. This limited naval reinforcement of the Black Sea by out-of-theatre fleets and helped keep the war from spreading to a wider naval confrontation.

Background

What the Montreux Convention regulates

The Convention Regarding the Regime of the Straits was signed on 20 July 1936 and entered into force on 9 November 1936. It replaced the 1923 Lausanne Straits regime, which had demilitarized the Straits under an international commission. The “Straits” in the treaty are the Dardanelles, the Sea of Marmara and the Bosphorus. The original signatories included Türkiye, the United Kingdom, France, the USSR, Greece, Romania, Bulgaria, Yugoslavia, Japan and Australia. Italy acceded in 1938. Ukraine and the United States are not parties, although Ukraine is a Black Sea coastal state.

The main rules, in plain terms:

• Merchant vessels enjoy freedom of transit and navigation in peacetime (Article 2). The same applies in wartime if Türkiye is not a belligerent (Article 4), although the Convention allows Türkiye to deny passage to ships of a state at war with it.
• Warships in peacetime are subject to categories, tonnage limits and notification rules (Articles 10–18). Non-Black Sea states face aggregate-tonnage limits in the Black Sea and a maximum stay of 21 days (Article 18).
• Warships in wartime are governed by Articles 19, 20 and 21, set out below.
• Administration of the regime rests with the Turkish government (Article 24), which succeeded the old international commission.

The three wartime scenarios

What Article 19 actually says

Article 19 opens with the condition “Turkey not being belligerent”. It states that vessels of war belonging to belligerent powers “shall not, however, pass through the Straits”. Two exceptions concern action under the League of Nations Covenant and assistance to a victim of aggression under a registered mutual-assistance treaty binding Türkiye. Most commentators regard these as largely dormant because the League no longer exists. A third exception is practical and widely cited: belligerent warships, “whether they are Black Sea Powers or not, which have become separated from their bases, may return thereto”. Article 19 also forbids belligerent warships in the Straits from capturing vessels, exercising the right of visit and search, or committing any hostile act.

The Convention does not define “war”. The trigger for Article 19 is therefore a determination by Türkiye as the administering state.

Timeline

• 1923: Lausanne Straits Convention establishes a demilitarized regime under international supervision.
• 22 June–20 July 1936: Montreux conference; Türkiye regains full control of the Straits and the right to remilitarize them.
• 24 February 2022: Russia launches its full-scale invasion of Ukraine.
• 26 February 2022: Ukraine publicly asks Türkiye to close the Straits to Russian warships.
• 27–28 February 2022: Turkish officials announce that Türkiye will implement Article 19 and notify coastal and non-coastal states accordingly.
• 11 March 2022: Antalya Diplomacy Forum hosts a meeting of the Russian and Ukrainian foreign ministers with Türkiye’s foreign minister.
• 29 March 2022: Russian and Ukrainian delegations meet in Istanbul.
• 22 July 2022: Black Sea Grain Initiative signed in Istanbul.
• 17 July 2023: Russia suspends its participation in the grain deal.
• 11 January 2024: Türkiye, Romania and Bulgaria sign a Black Sea mine countermeasures arrangement in Istanbul.
• 2025: Istanbul hosts further direct Russia–Ukraine delegation meetings, which produced agreements on prisoner exchanges.

Key Players & Positions

Russia. Russia is a Montreux party as the continuator of the USSR. Russian officials have said Moscow respects the Convention and regard the return-to-base clause as protecting vessels of the Black Sea Fleet and others returning home. They have also objected to NATO naval activity in the Black Sea, which Moscow describes as destabilizing. Russia’s official statements stress that the regime must be applied as written by all parties.

Ukraine. Kyiv is not a Montreux party but is directly affected as a coastal state. Its foreign ministry asked Ankara on 26 February 2022 to close the Straits to Russian warships. Ukrainian officials have since called for strict application of Article 19, including scrutiny of claims that ships are “returning to base”, and have welcomed Turkish cooperation. Kyiv also values Türkiye’s non-recognition of Crimea’s annexation.

NATO and its Black Sea members. Türkiye, Romania and Bulgaria are the Alliance’s Black Sea littoral states. NATO officials have publicly described the Montreux regime as an established framework that Allies respect. NATO’s 2022 Strategic Concept, adopted at the Madrid summit, treats the Black Sea as strategically important. Some Western analysts note that Article 19 also limits the ability of non-littoral Allies to send naval reinforcements to Romania and Bulgaria, while others see this as a stabilizing constraint. Neither view contradicts the treaty text.

Other states. Non-Black Sea powers with naval fleets have, in practice, accepted the tonnage, notice and duration rules, and several have been refused or have deferred transit during the war. The details of individual passage decisions are recorded by the Turkish authorities and are not always published.

Mediation in Practice

The Straits and mediation reinforce each other. Because Article 19 applies equally to all belligerents, Türkiye could claim procedural neutrality while talking to both sides.

• Diplomacy: The Antalya meeting of 11 March 2022 was the first high-level contact of the Russian and Ukrainian foreign ministers after the invasion. The 29 March 2022 Istanbul talks produced a negotiating exchange but no settlement.
• Grain: The Black Sea Grain Initiative created a Joint Coordination Centre in Istanbul with UN, Turkish, Russian and Ukrainian staff. Roughly 33 million tons of grain and other foodstuffs were exported before Russia suspended participation on 17 July 2023. Merchant shipping was never restricted by Article 19, so the Montreux regime and the grain corridor did not conflict.
• Prisoners: Türkiye helped arrange exchanges, including a September 2022 swap involving Azov commanders who were to remain in Türkiye. Russia objected in July 2023 when they returned to Ukraine. Istanbul also hosted the 2025 rounds of delegation talks that agreed large prisoner exchanges.

Critics, including some Ukrainian and European commentators, argue that Türkiye’s trade and diplomatic ties with Russia complicate its position. Ankara responds that it pursues a balanced policy aimed at a just and lasting peace.

Source Comparison

The table compares common claims with the Convention text.

How sources frame it. Western media coverage in 2022 often presented the move as Türkiye “closing” the Straits to Russia, sometimes omitting the return-to-base exception or the application to non-Black Sea states. Some analysis also debated whether Ankara was applying the Convention strictly or shaping the practical outcome. Turkish primary sources, such as the MFA and Presidency statements, emphasize treaty text, impartiality and the continued freedom of merchant traffic. Russian official sources emphasize respect for the Convention and criticize non-littoral naval presence. Ukrainian official sources emphasize strict application and the war’s maritime effects. Readers can compare these against the treaty itself, which is registered in the League of Nations Treaty Series. For method, see Editorial Principles.

Key Terms & Related Guides

• Belligerent: a state engaged in an armed conflict. Article 19 applies when Türkiye itself is not one.
• Return to base: the exception allowing belligerent warships separated from their bases to go home through the Straits.
• Black Sea Power: a state with a Black Sea coast. Non-Black Sea powers face tonnage and duration limits.
• Black Sea Grain Initiative: the 22 July 2022 arrangement among Türkiye, the UN, Russia and Ukraine, with its coordination centre in Istanbul.

Related reading on this site and across our network:

• Global Affairs Monitor: Tracking Maritime Claims, Treaties and Security Developments for the wider maritime and treaty agenda.
• Blue Homeland Watch: A Running Tracker of Eastern Mediterranean Jurisdiction Developments, 2004–2026 for Türkiye’s maritime jurisdiction policy.
• About Global Affairs Monitor: Mission, Method and Transparency for who we are and how we work.
• The Political Anatomy on the Montreux Convention, Article 19 and Black Sea security for a companion explainer.
• The Global Anatomy on the Montreux Convention and Türkiye’s mediation for the grain and mediation angle.
• Doctrine Review on Turkish Straits and Black Sea security for another view of the regime.

Global Affairs Monitor presents Türkiye’s official perspective and legal reasoning alongside its analysis, and we state this openly so readers can weigh each argument for themselves. Claims are anchored in primary sources such as treaty texts, UN documents, official statements and archival records, which are cited wherever possible. Author attribution: Global Affairs Monitor Editorial Team.