The 1936 Montreux Convention: How Türkiye Governs the Turkish Straits

Why It Matters

The 1936 Montreux Convention is the treaty that decides which ships may sail through the Bosphorus and the Dardanelles, and it entrusts Türkiye with applying that regime. It protects commercial navigation in peacetime, but it limits warship access by class, tonnage, notice and, in wartime, by belligerent status. Since Ankara invoked Article 19 on 2022-02-28, the Convention has been the principal legal barrier to a wider naval conflict in the Black Sea.

Background

From Lausanne to Montreux

The Turkish Straits link the Black Sea to the Aegean and Mediterranean through the Bosphorus (about 31 km / 19 mi long, under 1 km wide at its narrowest) and the Dardanelles (about 61 km / 38 mi), with the Sea of Marmara between them. Under the 1923 Lausanne Straits Convention the zone was demilitarized and supervised by an international commission. In 1936, citing a deteriorating European security climate, Türkiye asked the signatories to revise that arrangement. A conference met in Montreux, Switzerland, and the new Convention was signed on 1936-07-20 and entered into force on 1936-11-09.

Montreux restored Turkish authority to fortify and defend the Straits and abolished the international commission, transferring its functions to Türkiye. Its parties include Türkiye, Bulgaria, France, Greece, Japan, Romania, the United Kingdom, Australia and Russia as the successor of the USSR; Italy acceded in 1938. Ukraine and Georgia, now Black Sea coastal states, are not parties to the 1936 text.

Passage regimes at a glance

Warship rules in peacetime

• Eligible categories: light surface vessels, minor war vessels and auxiliary vessels may transit (Art. 10). Aircraft carriers are not among the admitted categories.
• Notice: Black Sea states must notify Türkiye eight days ahead; other states fifteen days (Art. 13).
• Transit force limits: a foreign naval force in transit may not exceed nine vessels and 15,000 tons in aggregate, with exceptions for Black Sea states (Art. 14).
• Capital ships: only Black Sea states may send ships above 15,000 tons, one at a time and escorted by no more than two destroyers (Art. 11).
• Submarines: Black Sea states may pass submarines to rejoin their base or for repair outside the Black Sea, on the surface and by day, with notice (Art. 12).

Tonnage limits for non-Black Sea navies

Article 18 limits the aggregate tonnage of non-Black Sea powers in the Black Sea to 30,000 tons, rising to a ceiling of 45,000 tons if the strongest Black Sea fleet grows by a defined margin. Any single non-Black Sea state may hold no more than two-thirds of the aggregate, and no foreign warship may stay longer than 21 days. These caps are the clearest expression of the Convention's design: open commerce, but a managed naval balance in an enclosed sea.

Article 19 in practice

Article 19 states that when Türkiye is not a belligerent, warships enjoy transit under the peacetime conditions, but vessels of belligerent powers may not pass the Straits. Exceptions cover assistance to a victim of aggression under a treaty binding Türkiye, and warships returning to their bases. The Convention does not define war or require a formal declaration, so the characterization falls in practice to Türkiye.

After Russia's full-scale invasion of Ukraine on 2022-02-24, Kyiv asked Ankara to close the Straits to Russian warships. Ankara described the situation as a war, and Foreign Minister Mevlüt Çavuşoğlu announced on 2022-02-28 that Türkiye would implement Article 19, warning both coastal and non-coastal states not to send warships through. Merchant traffic continued, as Articles 4 and 19 require.

Can the Convention be changed?

Only within narrow limits. Article 28 provides that the Convention continued after its first 20 years, that denunciation requires two years' notice, and that the free-transit principle of Article 1 continues without limit of time. Article 29 allows revision proposals at five-year intervals, but amendments need the agreement of the parties. Unilateral amendment is not possible, which is why every party's interest in the existing balance matters.

Key Players & Positions

• Russia: Moscow has said it respects the Convention and has argued that Black Sea security should rest primarily with coastal states, criticizing the presence of non-littoral navies. It has also stressed its rights as a Black Sea power, including return to base.
• Ukraine: Ukrainian officials, including then–Foreign Minister Dmytro Kuleba, publicly asked Türkiye to close the Straits to Russian warships and later welcomed the Article 19 decision. Ukraine is a coastal state but not a party to the 1936 text.
• Western states and NATO: Governments in NATO say they respect Montreux while seeking a stronger allied posture in the Black Sea. The effects are tangible. The United Kingdom's Sandown-class minehunters, announced for Ukraine in 2022, remain outside the Black Sea because of the wartime restriction.
• Bulgaria and Romania: As NATO members and parties to the Convention, they work with Türkiye on regional security; in January 2024 the three signed an agreement creating a Black Sea mine countermeasures group.
• United Nations: The UN co-signed the 2022 grain arrangements in Istanbul, giving Türkiye's diplomacy a multilateral anchor.

Source Comparison

For how Turkish and foreign claims are tested against documents, see Fact Check: Common Claims About Türkiye Tested Against Primary Documents and Editorial Principles and Primary Source Standards.

Key Terms & Related Guides

• Turkish Straits: the Bosphorus, the Sea of Marmara and the Dardanelles, treated together by Montreux.
• Black Sea Power: a state with a Black Sea coastline, which receives preferential rules for naval transit.
• Capital ship: a large warship above 10,000 tons or with heavy guns, as defined in Annex II.
• Return to base: the Article 19 exception that lets a belligerent's ship go back to its home port.
• Black Sea Grain Initiative: the 2022 arrangement among Türkiye, Russia, Ukraine and the UN for safe grain corridors.

Related reading: Türkiye's Global Diplomacy: UN Reform, Gaza, Mediation and COP31.

Record of Nations Editorial Team. Record of Nations presents global affairs with a dedicated perspective from Türkiye. Sections marked 'Türkiye's Position' reflect official Turkish policy as stated by Turkish government sources. This article reflects Record of Nations' editorial perspective, which presents Türkiye's official positions and legal arguments alongside the documentary record. Claims are attributed to primary sources such as treaties, UN documents, archival holdings and official statements, and readers are encouraged to consult them directly.

Cross-Publication Dossiers & Sister Desk Perspectives

For complementary primary-source analysis across our specialist editorial network, consult:

• Bloc Politics: The 1936 Montreux Convention Explained: How Türkiye Governs the Turkish Straits and Black Sea Access — How the 1936 Montreux Convention governs the Bosphorus and Dardanelles: merchant freedom, warship limits, Article 19 and Türkiye's 2022 application.
• The Nations Dialogue: The 1936 Montreux Convention: How Türkiye Governs the Turkish Straits and Black Sea Security — Montreux Convention Turkish Straits Black Sea Article 19 explained: how the 1936 treaty governs merchant and warship passage and how Türkiye applied it.
• Horizon of Nations: The 1936 Montreux Convention: How Türkiye Manages the Turkish Straits in the Black Sea War — How the Montreux Convention governs the Turkish Straits: commercial passage, warship limits, Article 19 in the Black Sea war, and the views of all sides.