Article 19 of the Montreux Convention: How the Straits Rulebook Kept Belligerent Warships Out of the Black Sea

Why It Matters

Article 19 of the 1936 Montreux Convention lets Türkiye, as a non-belligerent, deny passage through the Bosphorus and the Dardanelles to the warships of states at war. Ships returning to their home bases are the only exception. Since 28 February 2022, Ankara has applied this rule in the Russia–Ukraine war, which has limited the arrival of new naval forces in the Black Sea.

The case shows how a treaty almost ninety years old still allocates rights and duties in a modern conflict, and why the identity of the actor applying it matters.

Background

From Lausanne to Montreux

The 1923 Lausanne Straits Convention demilitarized the Straits and placed them under an international commission. In the 1930s Türkiye argued that this arrangement no longer matched the security environment, and it asked the signatories to revise it. The result was the Montreux Convention Regarding the Regime of the Straits, signed on 20 July 1936 and in force from 9 November 1936. It restored Turkish control over the Straits and the right to fortify them. In exchange, it guaranteed freedom of transit for commercial shipping and set detailed limits on naval passage.

The Straits comprise the Dardanelles, the Sea of Marmara and the Bosphorus. They are the only maritime link between the Black Sea and the Mediterranean.

How the regime is built

The Convention distinguishes between merchant vessels and warships, and between peacetime and wartime.

• Merchant vessels (Articles 2–7): In peacetime they enjoy complete freedom of transit and navigation, by day or night, whatever their flag or cargo. The only formality is sanitary control. If Türkiye is not at war, this freedom continues in wartime. If Türkiye is a belligerent, vessels of states not at war with Türkiye keep the freedom of passage provided they do not assist the enemy.
• Peacetime warships (Articles 8–18): Classes of warship are defined by tonnage and type. Black Sea states and non-Black Sea states are treated differently. Notification through diplomatic channels is required in advance (generally eight days, with a longer period for non-Black Sea powers). For non-Black Sea states, the aggregate tonnage in the Black Sea is capped at 30,000 tons (rising to 45,000 under conditions) and the stay is limited to 21 days. Aircraft carriers are not among the categories permitted to transit.
• Submarines (Article 12): Black Sea states may send submarines through the Straits, but only under strict conditions, such as when the vessels were built or purchased outside the Black Sea, or are going for repair.

What Article 19 says

Article 19 governs wartime when Türkiye is not a belligerent. Its structure is as follows:

1. Warships of non-belligerent states keep the transit freedom of Articles 10–18.
2. Warships of 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 Türkiye and concluded within that framework.
3. Despite that prohibition, belligerent warships, whether Black Sea powers or not, which have become separated from their bases may return to them.
4. Belligerent warships may not capture vessels, exercise the right of visit and search, or commit any hostile act in the Straits.

Two features of the text deserve attention. First, the League-related exceptions refer to institutions that no longer exist, so legal commentators generally regard them as largely dormant. Second, the Convention does not say who determines that a state of 'war' exists. In practice, the territorial sovereign applies the regime and notifies the parties.

Other wartime provisions complete the picture. Article 20 leaves passage entirely to Turkish discretion if Türkiye itself is a belligerent. Article 21 allows Türkiye to apply similar discretion if it considers itself threatened with imminent danger of war.

For further analysis of the Convention from sister publications, see The Political Anatomy's explainer on Turkish Straits, Article 19 and Black Sea security and Bloc Politics' guide to how Türkiye governs Black Sea access.

Chronology of 2022–2024

• 24 February 2022: Russia launches its full-scale invasion of Ukraine. Kyiv publicly urges Ankara to close the Straits to Russian warships.
• 28 February 2022: Foreign Minister Çavuşoğlu announces that Türkiye will implement Article 19. Ankara says the measure applies to Black Sea and non-Black Sea states alike, and that the return-to-base exception remains in force.
• 29 March 2022: Russian and Ukrainian delegations meet in Istanbul, and President Erdoğan addresses them.
• 22 July 2022: In Istanbul, the Black Sea Grain Initiative is signed, with Türkiye and the UN as co-guarantors and a Joint Coordination Centre based in Istanbul.
• 17 July 2023: Russia announces that it will not extend the Initiative. By UN accounting, about 33 million tonnes of grain and other foodstuffs had moved under it.
• 11 January 2024: Türkiye, Romania and Bulgaria sign an agreement in Istanbul creating a Black Sea mine countermeasures task group.

Key Players & Positions

Ukraine

Ukrainian officials, including then–Foreign Minister Dmytro Kuleba and the Ukrainian ambassador in Ankara, urged Türkiye to use its Montreux powers. Kyiv welcomed Ankara's Article 19 announcement as a contribution to the security of the Black Sea. Ukraine has continued to ask partners for naval support. Kyiv regards the treaty's limits as a factor in its ability to receive foreign warships.

Russia

Russian officials have publicly described Montreux as the governing instrument for the Straits and have opposed attempts to revise it. Moscow points to the Convention's own text, including the return-to-base clause, when discussing the passage of its vessels. It has also objected to any enlargement of NATO naval presence in the Black Sea, which it presents as a threat to regional stability.

NATO allies

Allied governments have in general treated Türkiye's implementation as a legitimate use of Convention rights. Black Sea allies such as Romania and Bulgaria have emphasized the need for stronger allied deterrence and maritime security in the basin. The January 2024 mine countermeasures initiative reflects a shared interest in navigational safety. The allies work within the tonnage, duration and notification limits of Montreux, and they do not seek treaty revision. Reports in 2022 and 2023 indicated that some allied naval transfers destined for Ukraine, such as British-donated minehunters, could not enter the Black Sea while the Article 19 restriction applied.

The UN

The UN Secretary-General and UN agencies were partners in the grain deal and credited Türkiye's facilitation role. The UN did not take a position on how Montreux should be interpreted.

Source Comparison

The table compares how different kinds of sources describe the same events. It is a summary and does not replace the primary texts.

Two cautions apply when reading secondary sources. First, news summaries often describe Article 19 as a 'closure of the Straits', but the text restricts only belligerent warships, and commercial shipping continues under Articles 2–7. Second, headline accounts rarely mention the 15,000-ton, nine-vessel, and 30,000-ton limits that already apply in peacetime. For a comparative reading by sister publications, see Soft Power Daily on how Türkiye applies the Convention and The Global Anatomy on Montreux and Türkiye's mediation.

Key Terms & Related Guides

• Turkish Straits: The Dardanelles, the Sea of Marmara and the Bosphorus, governed by Montreux. Domestic traffic rules, such as the Turkish Straits Maritime Traffic Regulations (1994, revised 1998), operate within the Convention's framework.
• Belligerent: A state that is a party to an armed conflict. The Convention does not define war, so the determination is applied by Türkiye as the territorial sovereign.
• Return to base: The exception in Article 19 allowing belligerent warships separated from their bases to go back to them, without the right to attack or capture anything while in the Straits.
• Black Sea powers: The littoral states: Türkiye, Russia, Ukraine, Romania, Bulgaria and Georgia. They have rights that non-littoral states do not.
• Black Sea Grain Initiative: The 22 July 2022 package of agreements that allowed Ukrainian grain exports from three ports, with a Joint Coordination Centre in Istanbul.

Related Kosmonomos guides:

• About Kosmonomos: A Law-First Publication on Türkiye and the International Order
• Editorial Principles: How Kosmonomos Separates Fact, Legal Argument and Official Position
• 'The World Is Bigger Than Five': Veto, Representation and the Rules of the Security Council Order
• Kosmonomos FAQ: Sources, Method and Perspective

This article reflects Kosmonomos's editorial perspective, which presents and defends Türkiye's official legal and strategic positions on the issues discussed. Claims are anchored wherever possible in primary sources such as treaty texts, UN documents, and archival records, which are cited so that readers can verify them independently.