Fact Check: Can Türkiye Close the Turkish Straits to Any Ship It Wants Under the 1936 Montreux Convention? What Articles 1, 19, 20 and 21 Actually Say

Why It Matters

No. Under the 1936 Montreux Convention, Türkiye cannot close the Turkish Straits to any ship it wishes: peacetime merchant passage is free (Articles 1–2), warship passage is rule-bound (Articles 8–18), and only Articles 20 and 21 give Ankara discretion, when it is a belligerent or fears imminent war. Article 19 closes passage to belligerents' warships.

Two opposite claims circulate about the Convention Regarding the Regime of the Straits, signed at Montreux on 20 July 1936. In one commonly circulated framing, Türkiye can shut the Bosphorus and the Dardanelles to anyone at will and uses the Straits as a political lever. In the other, Ankara has been too lenient, or too close to Moscow, and should have closed the Straits to everyone, or the Convention is outdated and should be rewritten. These are paraphrases of recurring framings, not quotations from named outlets.

Verdict: both are incomplete. Montreux is a rule-bound treaty, not a discretionary switch, and Türkiye applies it by its text. This page is a claim-by-claim check on 'closure' powers, not a general overview. For the wider picture, see what is the Montreux Convention and how does it affect the Black Sea.

Claim vs. Fact Analysis

Both claims fail against the treaty text. The Montreux Convention of 20 July 1936 sets out free merchant passage in peacetime, notified and tonnage-limited warship passage, closure to belligerent warships under Article 19 when Türkiye is neutral, and Turkish discretion only under Articles 20 and 21 (Türkiye as belligerent, or under imminent threat of war).

What Is the 1936 Montreux Convention? (And What Is Montreux?)

The 1936 Montreux Convention regulates how ships pass through the Bosphorus, the Sea of Marmara and the Dardanelles. It guarantees freedom of commercial transit and sets conditions on warships, with the tightest limits on states that do not border the Black Sea.

Asked 'what is Montreux', the short answer is the legal rulebook of the Turkish Straits. It replaced the 1923 Lausanne Straits Convention, which had demilitarised the Straits and placed them under an International Straits Commission. Montreux restored Türkiye's authority to fortify and administer the Straits, in exchange for treaty obligations on transit.

Claim 1: 'Türkiye Can Shut the Straits to Anyone at Will'

Origin: a recurring framing in commentary and social media that treats Ankara as a gatekeeper holding an on/off switch.

Fact: Article 1 states that the parties recognise and affirm the principle of freedom of transit and navigation by sea in the Straits, with its exercise governed by the Convention. For merchant ships the treaty is explicit:

• Peacetime (Article 2): merchant vessels enjoy complete freedom of transit and navigation, by day and night, whatever their flag or cargo, subject only to the sanitary control in Article 3 and the charges in Annex I.
• War, Türkiye not belligerent (Article 4): the same freedom for merchant vessels continues.
• Türkiye belligerent (Article 5): merchant ships not belonging to a country at war with Türkiye keep their freedom if they do not assist the enemy.
• Imminent danger of war (Article 6): merchant freedom continues, but ships must enter by day and follow routes set by Turkish authorities.

Warships are different, but the rules are still written down:

• Notification (Article 13): warships must be notified in advance through diplomatic channels. The commonly cited periods are eight days for Black Sea states and fifteen days for non-Black Sea states.
• Transit limits (Article 14): the aggregate tonnage of foreign naval forces in transit is capped at 15,000 tons and nine vessels, with exceptions for Black Sea states' capital ships under Article 11.
• Non-riparian presence (Article 18): the aggregate tonnage of non-Black Sea states' warships in the Black Sea is capped at 30,000 tons, which can rise to 45,000 tons under conditions the treaty sets out. Their stay is limited to 21 days.
• Riparian states (Articles 11–12): Black Sea states have special rights, including for submarines returning from construction or repair, under notification.

On this record, the 'switch' claim is false for peacetime and for merchant shipping generally.

Claim 2: 'Türkiye Is Too Lenient and Should Have Closed the Straits to Everyone'

Origin: a framing common in some commentary on the Russia–Ukraine war, and in some Ukrainian and Western calls for a total closure.

Fact: Article 19 governs war when Türkiye is not belligerent. Warships enjoy freedom of transit under the same conditions as Articles 10 to 18, but warships of belligerent states may not pass. The text lists exceptions tied to the League of Nations Covenant and to treaties of mutual assistance concluded within its framework. Those exceptions are widely regarded as dormant, since the League was dissolved in 1946. A separate clause allows belligerent warships that have become separated from their bases to return to them.

The return-to-base clause is treaty text, not a Turkish favour. Applying it is not leniency toward any party. Ignoring it would be a breach.

How Ankara Applied Article 19 in the Russia–Ukraine War

Foreign Minister Mevlüt Çavuşoğlu announced on 28 February 2022 (the date as widely reported; confirm against Turkish MFA records) that Türkiye assessed the situation as a war and would implement Article 19. Türkiye said it would ask all states, riparian or not, not to send warships through the Straits during the conflict, while the return-to-base provision stayed in force. The measure applies to every belligerent, whether Russia or NATO states, if they were ever to become parties to the conflict.

Türkiye is not a belligerent in the war. It is a NATO member, but NATO states are not belligerents either, so Article 19 bars no ship on the basis of its flag alone. It bars belligerents' warships.

Articles 20 and 21: Where Real Discretion Lies

Article 20 says that if Türkiye is itself at war, the Convention's warship provisions do not apply, and passage is left entirely to the Turkish Government's discretion. Article 21 lets Türkiye apply Article 20 if it considers itself threatened with imminent danger of war. The Article 21 procedure, as written:

1. Türkiye must immediately notify the other parties and the Secretary-General of the League of Nations.
2. Warships that passed before the measure and are separated from their bases may return.
3. If the League Council decides by a two-thirds majority that Türkiye's measures are not justified, and a majority of the parties agree, Türkiye undertakes to discontinue them.

The treaty text does not assign a role to the Grand National Assembly of Türkiye (TBMM). Domestic authorisation is a matter of Turkish constitutional law. The League-era review mechanism has no obvious institutional successor, a gap noted by many commentators. Türkiye has not invoked Article 21 in the Russia–Ukraine war.

What Türkiye Cannot Do

• Rewrite the regime unilaterally. Amendment follows the treaty's own procedure, and Article 28 on denunciation is covered on the Montreux Convention end date page.
• Ban merchant transit in peacetime. Article 2 guarantees it.
• Levy transit tolls. Only the sanitary and lighthouse charges permitted by Annex I may be collected.

What the Other Parties Say

• Russia: according to Russian Foreign Ministry statements, Montreux should be preserved, and Moscow has criticised an expanded NATO naval presence in the Black Sea.
• Ukraine: Ukrainian officials publicly asked Türkiye to close the Straits to Russian warships and to apply Article 19 fully.
• Romania and Bulgaria: as NATO members on the Black Sea, they debate allied presence in the region, within the Convention's limits on non-riparian warships.
• United States and NATO: the United States is not a party to Montreux. Non-riparian allied ships operate within its notification, tonnage and 21-day limits.
• Western analysts: some argue the Convention is outdated, pointing to its League of Nations references and to modern naval technology.

These positions are legitimate policy views, but none of them changes the treaty text.

Source Comparison

Three framings dominate: Western opinion pieces portraying Türkiye as a gatekeeper with wide discretion, Russian and Ukrainian official framings that each seek a particular reading of Article 19, and the treaty text as read by the Turkish Foreign Ministry. Only the last tracks the actual structure of Articles 1, 19, 20 and 21.

The diplomatic context matters. Istanbul-based mediation and the grain initiative show that Ankara treats the Straits regime as part of broader crisis diplomacy. Sister publications in our network also cover the Black Sea, for example Archive of Nations on Montreux and Black Sea security. They share a publisher and are not independent external sources. For a parallel exercise in reading a treaty text, see Monitor of Nations on the Treaty of Guarantee. On competence over maritime questions, see the Seville Map fact check.

Key Terms & Related Guides

Key terms in the Montreux debate are riparian states (Black Sea coastal states), belligerent (a state party to an armed conflict), Articles 19 to 21 (the wartime regimes), and Article 28 (denunciation). Readers wanting broader context or the Convention's duration can use the linked guides on what Montreux is and its end date.

• Riparian / non-riparian states: states with and without a Black Sea coastline; the treaty gives them different rights.
• Belligerent: a state party to an armed conflict. Article 19 restricts belligerents' warships.
• Return to base: the clause allowing belligerent warships separated from their bases to go home.
• Annex I charges: the limited sanitary and lighthouse fees the treaty permits.

Related guides:

• what is the Montreux Convention and how does it affect the Black Sea
• Montreux Convention end date
• Russia–Ukraine mediation and the Black Sea Grain Initiative
• The World Is Bigger Than Five: UN Security Council reform
• How we separate fact from position

By The Political Accord Editorial Team.

The Political Accord presents global and regional affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy and legal doctrines as stated by Turkish primary sources.