Montreux Article 19 in Practice: How Türkiye Closed the Straits to Belligerent Warships in 2022

Why It Matters

Article 19 of the 1936 Montreux Convention says that when Türkiye is not a belligerent, warships of states at war may not pass through the Turkish Straits, with one practical exception: vessels returning to their home bases. In February 2022 Türkiye determined that the Russia–Ukraine conflict was a war within the meaning of the Convention and applied the ban to all belligerents. The decision shaped who could reinforce the Black Sea, and it is the legal backbone of Ankara's claim to have kept the war from spreading at sea.

Background

What the 1936 Convention Says

The Convention Regarding the Regime of the Straits was signed at Montreux on 20 July 1936 and entered into force on 9 November 1936. It replaced the Straits arrangements of the 1923 Treaty of Lausanne, which had demilitarized the Straits and placed them under an international commission. Türkiye had asked for revision because of rising instability in Europe, and the Convention restored Turkish control and military presence over the Bosporus, the Sea of Marmara and the Dardanelles.

The treaty rests on two ideas. Article 1 affirms freedom of transit and navigation by sea in the Straits. The rest of the text then balances that freedom with Turkish security and the interests of the Black Sea states, mainly through rules on warships.

• Merchant vessels: Peacetime passage is free (Article 2). If Türkiye is not at war, merchant ships of all flags keep that freedom in wartime as well (Article 5).
• Peacetime warships: Black Sea states have wider rights. Non-Black Sea states face notification requirements, per-ship tonnage limits, an aggregate tonnage ceiling in the Black Sea and a maximum stay of 21 days (Articles 13–18).
• Wartime, Türkiye neutral: Article 19 governs (see below).
• Türkiye at war or threatened: Articles 20 and 21 give Ankara wide discretion over passage.

Article 19 in Plain Language

Article 19 has four operative elements:

1. If Türkiye is not a belligerent, warships generally enjoy the same freedom of transit as in peacetime, under the conditions of Articles 10 to 18.
2. Warships belonging to belligerent powers may not pass through the Straits. The text carves out cases arising from the application of the Covenant of the League of Nations, and assistance to a victim of aggression under a mutual assistance treaty binding on Türkiye and concluded within that framework. Because the League was dissolved in 1946, most commentators regard this carve-out as practically inoperative.
3. Belligerent warships that have become separated from their bases may return to them, whether or not their flag state is a Black Sea power.
4. Belligerent warships may not capture ships, exercise the right of visit and search, or commit any hostile act in the Straits.

One structural point matters for the 2022 debate. The Convention leaves it to Türkiye, as the state controlling the Straits, to assess whether a war exists and how the provisions apply in practice.

Timeline of the 2022 Application

For the wider treaty architecture, see the sister-site explainers The Political Anatomy on Montreux, Article 19 and Black Sea security and Soft Power Daily on how Türkiye applies the Convention.

What Changed on the Water

Because Russia's Black Sea Fleet was already largely based inside the Black Sea, the main practical effect was to prevent reinforcement and rotation from outside, whether from Russia's Baltic, Northern or Pacific fleets or from any other belligerent. It also kept non-belligerent third-country navies subject to Türkiye's case-by-case reading. Turkish officials have described the policy as applying to every state at war, and the return-to-base exception was honoured for ships that qualified. Reporting at the time, including by Western agencies, noted that Ankara asked for evidence that ships seeking to pass were genuinely returning to base.

One widely discussed example involved Ukraine's own prospective naval reinforcements. Two former Royal Navy Sandown-class minehunters that the United Kingdom agreed to transfer to Ukraine could not enter the Black Sea while the wartime restrictions applied, according to British and Ukrainian officials.

Key Players & Positions

Russia. Russian officials have said publicly that Russia respects the Convention and have emphasized the legal legitimacy of the return-to-base exception. Moscow has separately criticized Turkish drone sales to Ukraine, which Ankara treats as a commercial and sovereign matter. Russia is also a Black Sea power and a signatory to the Convention, so any change to the regime would require its consent as well.

Ukraine. Kyiv asked Türkiye to close the Straits to Russian warships in the first days of the invasion, and its Foreign Ministry welcomed Ankara's decision. Ukrainian officials have since pressed for the strictest reading and for broader maritime security measures in the Black Sea. As a Black Sea state with limited naval strength, Ukraine also saw its own plans to acquire foreign vessels affected by the same wartime rules.

NATO allies and the West. Governments of NATO states generally treated the decision as a lawful exercise of Türkiye's Convention rights. Two debates ran through Western commentary: whether the regime in practice restricts allied naval support more than it hampers Russia's already-stationed fleet, and whether the return-to-base exception left a loophole. Romania and Bulgaria, NATO members and Black Sea riparians, have an interest in the regime remaining stable, as does Greece, a signatory.

Other Black Sea and signatory states. Georgia, Romania and Bulgaria have prioritized safe commercial navigation and demining. Most of the 1936 signatories have not called for reopening the text, and the Convention has since been joined by further states such as Italy, which acceded in 1938.

For the Turkish-law context of maritime jurisdiction beyond the Straits, see The Equity Principle at Sea: How Islands, Coastlines and Proportionality Shape Türkiye's Continental Shelf Case.

Source Comparison

The tension is real: legal commentary tends to agree on the text but to differ on judgment about its effects. For parallel treatments see The Global Anatomy on Montreux and mediation and Regional Balance on the Black Sea and Russia–Ukraine mediation. To see how this site treats such sources, read Editorial Principles and Primary Source Standards.

Key Terms & Related Guides

• Turkish Straits: The Bosporus, the Sea of Marmara and the Dardanelles, the only maritime link between the Black Sea and the Mediterranean.
• Belligerent: A state engaged in an armed conflict. Under Article 19, belligerent warships are barred from transit when Türkiye is neutral.
• Return to home base: The Article 19 exception allowing belligerent warships separated from their bases to go back to them.
• Black Sea power: A state with a Black Sea coastline. Montreux gives such states wider peacetime warship rights than non-riparian states.
• Articles 20 and 21: Provisions that give Türkiye discretion over passage if it is itself at war or considers itself threatened with imminent danger of war.

Related reading on this site: About The Quiet Argument: Mission, Perspective and Transparency, the Reader FAQ on sources and method, and the home page for the full set of doctrine guides.

Perspective Note

The Quiet Argument presents these analyses from a Türkiye-informed perspective, setting out Ankara's official doctrines alongside the legal and historical reasoning behind them. Claims are tied wherever possible to primary sources such as treaty texts, UN documents, archival records and official statements, so readers can verify them independently.

Published by The Quiet Argument Editorial Team.