Fact Check: Can Türkiye Close the Straits to Anyone It Wants? What the Montreux Convention Actually Permits

Why It Matters

No, Türkiye cannot close the Bosphorus and Dardanelles to whomever it wishes, and no, it is not a mere clerk with no authority. The 1936 Montreux Convention Regarding the Régime of the Straits gives Türkiye the role of administering a rules-based system. Merchant passage is free in peacetime. Warship passage is regulated by fixed numbers, tonnages and notice periods. Türkiye's own discretion widens only in two defined situations: when it is at war, or when it considers itself under imminent threat of war.

The issue became prominent again after the Russian invasion of Ukraine in February 2022, when headlines alternately claimed that Ankara had “closed the Straits” or that it was powerless to stop anything. Both framings misread the treaty. This fact check separates the text from the commentary.

Claim vs. Fact Analysis

Where the claims come from

Two opposite narratives circulate in media and commentary. The first holds that Türkiye is the “gatekeeper” that can switch the Straits on or off for political reasons. It appears in headlines such as “Turkey closes the Straits” and in commentary about Ankara’s leverage over Russia and NATO. The second holds that Montreux gives Ankara only administrative functions, so any restrictions it applies are optional or political. Related disputes recur around the proposed Kanal Istanbul project, which some commentators say could be used to bypass the Convention. The April 2021 public declaration by 104 retired Turkish admirals defending Montreux drew wider attention to that debate.

Both narratives are tested below against the Convention’s text. For background on the system as a whole, see our guide to the Turkish Straits and the Black Sea corridor and the sister-site explainer from Region Scope.

Claim 1: “Türkiye can open or close the Straits whenever it chooses”

Verdict: False for peacetime and for merchant shipping; partly true only in the narrow situations the treaty defines.

• Article 1 records the parties’ recognition of the principle of freedom of transit and navigation by sea in the Straits.
• Article 2 provides that in time of peace merchant vessels enjoy complete freedom of transit and navigation, by day and night, whatever their flag or cargo, without formalities beyond those in Article 3 (sanitary controls). The treaty’s merchant-shipping provisions (Section I) also protect passage in wartime in defined circumstances, so a blanket closure to commercial traffic is not a lawful option for a neutral Türkiye.
• Articles 8–18 regulate warships in peacetime. They distinguish Black Sea states from non-Black Sea states, cap transit tonnage, require advance notification, and limit how long non-Black Sea warships may stay in the Black Sea.
• Articles 20–21 are the exceptions. If Türkiye is a belligerent, the peacetime limits cease to apply and passage is left to Türkiye’s discretion. Article 21 allows Türkiye to apply the same powers if it considers itself threatened with imminent danger of war.

In short, discretion exists, but it is a defined legal category, not a general power. Türkiye is not a belligerent in the Russia–Ukraine war, so the Article 20–21 powers are not engaged.

Claim 2: “Türkiye has no real authority under Montreux”

Verdict: Also false. The Convention allocates real administrative and legal functions to Türkiye:

• Article 24 transfers the functions of the former International Straits Commission, created under the 1923 Lausanne regime, to the Turkish Government. Montreux thereby ended international administration of the Straits and restored Turkish control, including the right to remilitarize the zone.
• Notification goes to Türkiye. Under Article 13 the Turkish Government must receive prior notice through diplomatic channels. The commonly cited periods are eight days for Black Sea states and 15 days for non-Black Sea states.
• Türkiye applies the tonnage and duration limits. Individual transit is limited, aggregate tonnage of foreign naval forces in transit is capped at 15,000 tons and nine vessels (Article 14), non-Black Sea states may keep only 30,000 tons in the Black Sea (up to 45,000 tons under a conditional increase), and stays may not exceed 21 days (Article 18).
• Türkiye must decide when Article 19 applies. Someone must determine that a war exists and that Türkiye is not a party to it. The Convention does not name another body to make that determination, which is why Ankara’s announcement in late February 2022 carried legal weight.

In short, Türkiye is both the administrator and, in the Article 19 context, the implementing authority. It is bound by the treaty, but within it, it must make real legal judgments.

Claim 3: “Türkiye broke Montreux in 2022”

Verdict: Not supported by the text, although the claim is made from opposite directions.

Ukrainian officials and some commentators urged Ankara to close the Straits to all Russian vessels. Russian officials and some commentators argued that applying restrictions was a political choice. Neither claim is accurate.

1. What Article 19 says. When Türkiye is not at war, warships otherwise enjoy transit under the Articles 10–18 conditions. Warships of belligerent powers, however, may not pass, except in cases arising from the League of Nations Covenant or assistance to a victim of aggression under a qualifying mutual-assistance treaty. The Article also prohibits hostile acts in the Straits.
2. The return-to-base exception. Article 19 states that belligerent warships separated from their bases may return to them. A ban on belligerent warships is therefore not absolute, and the exception lets such vessels go home.
3. What Ankara did. On 28 February 2022, Foreign Minister Mevlüt Çavuşoğlu announced that Türkiye considered the situation a war and would implement Article 19 for all parties. Ankara has said the exception remains available only to ships genuinely returning to their home bases.
4. What it did not do. It did not close the Straits to merchant shipping, and it did not apply Articles 20–21. The grain exports under the 2022 Black Sea Grain Initiative, brokered in Istanbul, moved precisely because merchant navigation stayed open. See our detailed explainer: Montreux Article 19 and the Russia–Ukraine War, and the sister-site analysis at The Global Anatomy.

Russia has its own position and challenges some interpretations, particularly regarding vessels and bases. A fair summary is that interpretive debates exist at the margins, but no party has documented a treaty breach by Türkiye.

Claim 4: “The Convention expires or has to be renewed”

Verdict: Misleading. Montreux entered into force on 9 November 1936. Article 28 provided an initial 20-year term. Under Articles 28–29, it continues in force unless a party denounces it, and denunciation takes effect after two years’ notice. Parties may also propose amendments at five-year intervals. No denunciation has occurred. The document refers to the League of Nations Council in certain provisions, and the League has long since dissolved. That is a drafting legacy commentators debate, but it has not changed the treaty’s operation. Renewal is therefore not required, and revision requires agreement, not unilateral action.

Quick reference: who may do what

Source Comparison

The most reliable method is to read Articles 2, 8–19, 20–21 and 28–29 alongside the Foreign Ministry’s statements. For additional treatments of the same treaty, see Soft Power Daily and Bloc Politics. For how we vet such claims, see our Editorial Principles and FAQ on sources and verification.

Key Terms & Related Guides

• Turkish Straits: the Bosphorus, the Sea of Marmara and the Dardanelles, the sole maritime link between the Black Sea and the Mediterranean.
• Black Sea states: states with coasts on the Black Sea, which receive different warship treatment from non-Black Sea states under Montreux.
• Article 19: the wartime provision, applicable when Türkiye is not belligerent, barring warships of belligerent powers, subject to limited exceptions including return to base.
• Articles 20–21: Türkiye’s discretionary powers when it is at war or considers itself threatened with imminent danger of war.
• Return-to-base exception: the right of belligerent warships separated from their bases to return to them.

Related guides:

• The Turkish Straits and the Black Sea Corridor: How the Montreux Regime Governs Passage in Peace and War
• Montreux Article 19 and the Russia–Ukraine War: Why Warships Cannot Enter the Black Sea
• The Middle Corridor: How Türkiye Links Central Asia, the Caucasus and Europe by Rail, Road and Sea
• The Strategic Corridor: Türkiye at the Crossroads of Energy, Trade, Security and Law
• Sister publication: Doctrine Review on the Montreux Convention

Perspective Note: The Strategic Corridor presents Türkiye's official perspective and legal position as a distinct analytical viewpoint, while clearly distinguishing it from opposing claims. Wherever possible, assertions are attributed to primary sources such as treaties, UN and UNESCO documents, court rulings and archival records.