Did Türkiye Close the Straits? Montreux Article 19 and Warship Access During the Russia–Ukraine War

Why It Matters

Article 19 of the 1936 Montreux Convention is the rule that decides which warships may enter the Black Sea when Türkiye is not at war but others are. After Russia's full-scale invasion of Ukraine in February 2022, Ankara applied it to every belligerent state, which kept the war's naval dimension largely out of the Black Sea from outside. Understanding what the article actually says, and what it does not, matters because the term 'closed the Straits' is widely used but is only partly accurate.

Background

The Montreux regime in brief

The Convention Regarding the Regime of the Straits was signed on 20 July 1936 and entered into force on 9 November 1936. It governs the Bosphorus, the Sea of Marmara and the Dardanelles, which together form the only maritime route between the Black Sea and the Mediterranean. It restored Turkish sovereignty over the Straits, including the right to remilitarize them, and replaced the 1923 Lausanne regime.

Its logic is tiered. Different rules apply depending on whether Türkiye is at peace, is not a belligerent but a war is under way elsewhere, or is itself at war or under imminent threat.

What Article 19 says

Article 19 begins with a general principle: if Türkiye is not a belligerent, warships enjoy freedom of transit and navigation under the same conditions as in peacetime. It then carves out warships of states at war. They may not pass the Straits except in two exceptional cases and one right of return:

• Covenant-based cases: situations arising from the League of Nations Covenant. These are historical in nature and have no practical application today.
• Assistance to a victim of aggression: under a treaty of mutual assistance binding Türkiye, concluded within the Covenant framework and registered under it. No such treaty is relevant to the 2022 war.
• Return to base: belligerent warships separated from their bases may go back to them.

The article also forbids belligerent warships from capturing vessels, exercising the right of visit and search, or carrying out any hostile act in the Straits. For the full treaty wording, consult the Convention text itself, as paraphrase is no substitute.

Two points are often missed. First, Article 19 restricts only warships of states at war, not all warships. Second, it does not touch merchant ships, which keep freedom of passage in wartime so long as Türkiye is not a belligerent.

Timeline: the 2022 application

For wider context on the Convention's operation, see The Turkish Straits as a Line of Power: Montreux, Black Sea Balance and Mediation and sister-publication explainers such as The Political Anatomy's guide to Article 19 and Black Sea security.

Key Players & Positions

Ukraine

Kyiv asked Türkiye to close the Straits to Russian warships at the outset of the invasion and has since welcomed the restriction while arguing that Russia should face stricter treatment. Ukrainian officials have pressed for the exceptions to be read narrowly, so that the return-to-base clause does not become a route for reinforcing Russia's Black Sea Fleet. Ukraine also cannot itself receive foreign warships through the Straits during the war, a consequence that has drawn comment from Ukraine's partners.

Russia

Russian officials have described Montreux as a respected, stable regime and have not mounted a formal legal challenge to Ankara's decision. Moscow's own framing of the conflict as a 'special military operation' has not altered Türkiye's legal assessment that a war exists. Russia's position in practice relies on the right of vessels to return to their bases, and on the fact that much of its Black Sea Fleet was already inside the Black Sea before the war began.

NATO and Western states

NATO officials have said the alliance respects the Montreux Convention, and Western governments have generally treated Türkiye's application as consistent with the treaty. Some Western commentary, however, notes an asymmetry: because Article 19 bars all belligerents, it limits reinforcement by Russia's other fleets but also limits Western naval support to Ukraine. Romania and Bulgaria, as Black Sea NATO members, have favoured stronger regional maritime security cooperation within the treaty framework.

Black Sea littoral and non-littoral states

Under Montreux, Black Sea powers enjoy certain privileges, such as the transit of capital ships above 15,000 tons under Article 11 and the submarine rules of Article 12. Non-littoral states face tonnage and duration limits. During the war, these distinctions mean that non-belligerent warships may still transit, but only within notification and aggregate-tonnage rules.

Source Comparison

The main gap between sources is vocabulary. International coverage often uses 'closure' for what the treaty treats as a defined restriction, while Turkish sources stress that the regime is neutral in design. For a parallel explanation, see Soft Power Daily on how Türkiye applies Montreux and Bloc Politics' explainer.

Key Terms & Related Guides

• Belligerent: a state engaged in an international armed conflict. Article 19 turns on whether a state is at war, a determination Türkiye made in February 2022.
• Return-to-base exception: the Article 19 provision allowing belligerent warships separated from their bases to go back to them.
• Capital ship: a warship above 10,000 tons, important for Articles 11 and 14.
• Black Sea power: a state with a Black Sea coastline, which receives privileges under Articles 11, 12 and 13.
• Article 20 / 21: the rules that give Türkiye discretion if it is itself at war or threatened with imminent war.

Related reading on Lines of Power:

• The Turkish Straits as a Line of Power: Montreux, Black Sea Balance and Mediation
• Defense Supply Chains as a Line of Power: How Türkiye Built Strategic Autonomy from Bayraktar to KAAN
• Lines of Power FAQ: Sources, Methodology and Perspective
• Editorial Principles: Sourcing Standards, Attribution and Corrections

For a cross-publication overview, see The Global Anatomy on Montreux and Türkiye's mediation.

Perspective Note

Lines of Power presents analysis from a Türkiye-informed perspective, arguing that Ankara's positions rest on treaty law, the UN Charter and documented historical record. Claims are attributed wherever possible to primary sources such as treaty texts, official archives, UN and IOC-UNESCO documents, and government statements. Sections marked 'Türkiye's Position' reflect official Turkish policy as stated by Turkish government sources. Published by the Lines of Power Editorial Team.