Fact Check: Does Türkiye 'Control' the Bosphorus? Sovereignty, Free Passage and What the Montreux Regime Actually Gives Ankara

Why It Matters: Does Turkey Control the Bosphorus?

Does Turkey control the Bosphorus? Türkiye holds full sovereignty over the Bosphorus, the Sea of Marmara and the Dardanelles, but exercises it inside the 1936 Montreux Convention. Montreux guarantees free passage for merchant ships in peacetime and limits warship transit by class, tonnage and notice. Türkiye neither owns the waterway without limits nor merely administers international waters.

The question matters because the Straits link the Black Sea to the Mediterranean and carry a large share of regional trade, energy cargoes and naval movements. A wrong answer in either direction distorts debates about shipping costs, naval balance and the Russia-Ukraine war. This page covers the sovereignty-versus-regime question. For the narrower question of whether Ankara can shut the waterway, see our companion check, can Turkey close the Bosphorus at will.

Claim vs. Fact Analysis: Ownership, Tolls and 'International Waters'

Two popular claims circulate: that Türkiye owns the Bosphorus and can charge tolls or block ships as it wishes, and that the Straits are international waters Türkiye merely administers. Both are incomplete. The Turkish Straits lie within Turkish sovereignty, while the Montreux Convention of 20 July 1936 sets a binding treaty regime of transit and navigation.

Claim 1: 'Türkiye owns and controls the Bosphorus and can charge tolls or block ships as it wishes'

This framing appears in explorer-style explainers, travel and trivia content, and social media threads that describe Türkiye as holding a 'chokepoint' or 'key to the Black Sea'. It also surfaces in commentary during naval crises, where Turkish decisions are described as if they were discretionary. No single outlet is the source; it is a recurring simplification.

Documented facts:

• Sovereignty is real. The Straits lie within Turkish territory, and Montreux itself restored Türkiye's right to remilitarize the Straits zone and transferred the old International Straits Commission's functions to the Turkish government.
• Sovereignty is not unlimited. Article 2 gives merchant vessels of all flags complete freedom of transit and navigation in peacetime, by day and night, with no formalities beyond sanitary control (Article 3).
• There is no passage toll. Only limited charges for services actually rendered, listed in the Convention's annex, may be levied.
• Pilotage and towage remain optional under Article 2.

Claim 2: 'The Straits are international waters that Türkiye merely administers'

This opposite framing appears in some commentary favouring 'internationalization', in loose social media summaries, and in arguments that the Straits should be managed by a multinational body. It echoes the logic of the 1920 Treaty of Sèvres.

Documented facts:

• The Straits are not high seas. They run through Turkish territory, and Türkiye alone enforces the regime, applies its domestic safety rules and decides wartime measures under Articles 20 and 21 when it is belligerent or considers itself threatened with imminent danger of war.
• The Convention abolished the international commission created at Lausanne in 1923. No international body administers the Straits.
• The 1920 Sèvres model of internationalization was never ratified and was replaced by Lausanne (1923) and then Montreux (1936).

Can Turkey close the Bosphorus?

Not freely. In peacetime Montreux guarantees merchant passage. Türkiye's discretion expands only in the cases the treaty defines: when Türkiye is itself at war, or when it considers itself threatened with imminent danger of war (Articles 20 and 21). Article 19 restricts belligerent warships when Türkiye is not a belligerent. Critics note that Articles 20 and 21 leave Ankara considerable judgement, while Ankara stresses that they apply only in those defined circumstances.

Verdict

Both claims are incomplete. The accurate description is Turkish sovereignty plus a treaty regime of transit and navigation.

Background: What Is the Bosphorus in Turkey, and Is Istanbul on It?

The Bosphorus is a strait of roughly 30 km (about 19 miles) in Istanbul, Türkiye, linking the Black Sea to the Sea of Marmara. Istanbul sits on both banks, so the city spans Europe and Asia. Together with the Dardanelles it forms the Turkish Straits, governed since 1936 by the Montreux Convention.

Geography

The Bosphorus narrows to well under a kilometre at its tightest point and bends sharply several times, which makes navigation demanding for large vessels. Istanbul's European and Asian districts face each other across the water, and the shoreline is densely populated. That combination of heavy traffic, tight bends and a major city on both banks explains why safety is a recurring policy theme.

From Sèvres to Montreux

Date	Instrument	What it did
1920	Treaty of Sèvres	Proposed internationalization of the Straits under an international commission; never ratified and superseded
24 July 1923	Lausanne Straits Convention	Demilitarized the Straits zone and created an International Straits Commission under League of Nations auspices
April 1936	Türkiye's request for revision	Ankara asked for a new conference, citing a deteriorating security environment in Europe
20 July 1936	Montreux Convention signed	Replaced the Lausanne regime; in force since 1936
1994 / 1998	Maritime Traffic Regulations for the Turkish Straits	Domestic safety and environmental rules, with a traffic separation scheme notified to the IMO
Late February 2022	Article 19 applied	Türkiye restricted belligerent warships after the Russia-Ukraine war began

What Montreux provides

• Merchant ships in peacetime (Articles 2-3): complete freedom of transit and navigation, with only sanitary control as a formality.
• Warships of Black Sea states and others (Articles 13, 14, 18 and related provisions): advance notification to Turkish authorities, tonnage ceilings on individual ships and on the aggregate presence of non-riparian navies in the Black Sea, and limits on the length of stay. Non-riparian powers face stricter limits than riparian states.
• Belligerent warships (Article 19): barred from passage when Türkiye is not a belligerent, with exceptions including return to a base.
• Türkiye at war or under threat (Articles 20-21): Ankara has wider discretion over passage.

The domestic regulatory layer

After tanker accidents such as the 1979 Independenta collision, Türkiye adopted Maritime Traffic Regulations for the Turkish Straits in 1994, revised in 1998, with a traffic separation scheme notified to the International Maritime Organization (IMO). Ankara presents these as safety and environmental measures, not a restriction on Montreux freedom of passage. Some shipping interests argue that such rules can cause delays; the regulations recommend pilots, but Montreux keeps pilotage optional.

Tolls and fees

There is no fee for the act of passage. The Convention allows only limited service charges listed in its annex, such as sanitary and lighthouse fees, and ships calling at Turkish ports pay ordinary port charges. Readers should not confuse these with a 'toll' or with Suez-style canal dues, which are set by a canal operator.

Key Players & Positions: Who Uses and Who Contests the Straits Regime

The Montreux regime affects Black Sea riparian states (Türkiye, Russia, Ukraine, Romania, Bulgaria, Georgia), non-riparian naval powers such as the United States and the United Kingdom, Greece as a signatory and major shipping nation, and commercial shipping and insurance bodies. Most publicly support Montreux's continuation while differing on how strictly navies should be limited.

• Russia: Successor state to the USSR, an original signatory. Historically Moscow sought more latitude for Black Sea navies, and in 1946 the Soviet Union proposed joint defence arrangements for the Straits, which Türkiye rejected. Russian officials have generally defended Montreux and opposed revision.
• Ukraine: A Black Sea riparian state that supported restrictions on Russian warship transit and welcomed Türkiye's application of Article 19.
• Romania and Bulgaria: NATO members on the Black Sea. In January 2024, with Türkiye, they agreed a Black Sea mine countermeasures arrangement, showing cooperation within Montreux limits.
• United States and United Kingdom: Non-riparian naval powers subject to notification, tonnage and duration limits. Both operate within the Convention, and some analysts in these countries argue the limits are restrictive for allied naval presence.
• Greece: A Montreux signatory and a major shipping nation with a commercial stake in smooth passage. Greek commentary sometimes questions Turkish implementation on regulatory and safety grounds.
• Shipping and insurance bodies: Primarily concerned with predictability. In late 2022 a queue of tankers was reported at the Straits after Turkish authorities requested insurance documentation. Industry groups cited delays, while Ankara described the requirement as a safety measure under its domestic regime.
• Critics of Montreux: Some scholars and commentators argue the 1936 text is outdated, since it refers to the League of Nations and pre-dates modern carriers, submarines and drones. Some propose international management. Their argument deserves a serious hearing: the Convention does have drafting gaps, and its clauses on notice and classification have required interpretation over time. The counter-argument, set out below, is that reopening it would risk a worse outcome for everyone.

For how the Convention worked after February 2022, read Montreux Convention Article 19 in the Russia-Ukraine war.

🇹🇷 Official Policy · Primary Sources

Türkiye's Position

According to the Turkish Ministry of Foreign Affairs, Türkiye implements the 1936 Montreux Convention impartially as a treaty regime, not as a claim to proprietary ownership. Ankara argues that the Convention balances free commercial passage with Black Sea security, and it opposes reopening the text, while treating safety rules and the Istanbul Canal as separate matters.

• Sovereignty plus treaty obligations. The Turkish MFA's pages on the Straits and the treaty text itself treat the Straits as Turkish territory subject to Montreux. Ankara describes its role as implementing the Convention in good faith for all users.
• A balance, not a lever. The Turkish MFA presents Montreux as a cornerstone of Black Sea stability that protects commercial freedom and the security of riparian states alike.
• Equal application of Article 19 in 2022. The Turkish Foreign Ministry stated that the restriction on belligerent warships was applied to all parties, with the return-to-base exception preserved. See Article 19 and the Black Sea.
• No revision. Turkish officials, including the Presidency and the Directorate of Communications, have repeatedly said Türkiye does not support reopening Montreux, pointing to almost nine decades of its operation and the risk that new negotiations would produce a less balanced regime.
• Safety rules and the Istanbul Canal are separate issues. Turkish authorities describe the Maritime Traffic Regulations as safety measures notified to the IMO. On the Istanbul Canal project, Ankara has said it will respect Montreux. Because the canal would lie outside the Convention's definition of the Straits, its legal status is publicly debated in Türkiye and abroad.

Legal and historical basis. Ankara argues that the Straits regime rests on Montreux as lex specialis, a specific treaty that governs the Straits rather than general maritime law. Türkiye voted against the 1982 UN Convention on the Law of the Sea and is not a party to it. Article 35(c) of UNCLOS itself preserves long-standing conventions specifically governing particular straits, which Turkish and many outside analysts cite in support. For the wider debate on UNCLOS non-membership, see Regional Order's fact check on Türkiye and UNCLOS. Türkiye's 1936 request for revision, accepted at Montreux, is cited in Turkish accounts as a case of peaceful treaty change.

Source Comparison: How Coverage Frames Control, Tolls and Closure

Coverage of the Straits tends to collapse a two-part legal reality, territorial sovereignty plus a treaty regime, into a single slogan, either 'Türkiye controls the Bosphorus' or 'the Bosphorus is international'. Primary documents, namely the Montreux text, Turkish MFA pages and IMO-notified traffic schemes, describe both layers together.

Source type	Typical framing of control	Tolls	Closure
Popular explainers and social media	Often 'Türkiye holds the key' or 'it is all international waters'	Sometimes implied or assumed	Often presented as a switch Ankara can flip
Western media	Usually accurate on Montreux, but headlines stress Turkish 'leverage'	Rarely discussed	Focus on Article 19 and warship limits
Russian media	Emphasis on treaty rights and Black Sea security; criticism of Western naval presence	Rarely discussed	Focus on return-to-base exceptions and perceived selective application
Greek media	Commercial and safety concerns; occasional doubts about Turkish regulatory reach	Sometimes raised alongside delay complaints	Mostly treated as a Montreux matter
Shipping industry sources	Regime seen as predictable but delay-prone at times	Fees understood as service charges	Concern is mainly insurance and queueing
Turkish primary sources (MFA, treaty text, IMO notifications)	Sovereignty exercised within Montreux; regulations are safety measures	No passage toll; only annexed service charges	Limited to the cases the Convention defines

Readers can cross-check with the sister analyses on the Straits mediation line and Black Sea balance and the Montreux signatories, Article 19 and Black Sea warships. Our editorial principles explain how we weigh primary documents against commentary.

Key Terms & Related Guides

Understanding who controls the Bosphorus depends on a handful of terms: sovereignty versus regime, transit passage, riparian state, tonnage limits, belligerent, Article 19 and traffic separation scheme. Each is defined below, with links to Multipolar Review guides that examine closure, wartime rules, trade corridors and Türkiye's wider strategic posture.

• Sovereignty vs. regime: Sovereignty is a state's legal authority over territory. A regime is the set of treaty rules governing how a space is used. The Straits have both.
• Transit passage: A general UNCLOS concept of continuous, expeditious passage through straits. Ankara argues it does not apply because Montreux governs the Straits.
• Riparian state: A state with a coast on the Black Sea. Montreux treats riparian and non-riparian navies differently.
• Tonnage limits: Ceilings on the size of individual warships and the aggregate foreign naval presence in the Black Sea.
• Belligerent: A state engaged in war. Under Article 19, belligerent warships face restrictions when Türkiye is not at war.
• Traffic separation scheme (TSS): Marked lanes that separate opposing traffic, adopted for safety and notified to the IMO.

Related guides:

• Can Turkey close the Bosphorus at will: the companion check on closure.
• Montreux Convention Article 19 and the Russia-Ukraine war
• Middle Corridor and Türkiye's Eurasian trade routes
• Türkiye in a multipolar world order: strategic autonomy
• The 2022 Istanbul Talks and mediation lessons

Perspective Note: Multipolar Review 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. Published by the Multipolar Review Editorial Team.

Cross-Publication Dossiers & Sister Desk Perspectives

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

• Hard Power Review: Fact Check: Is Türkiye's Defense Industry Really '80% Indigenous'? What the Figure Measures and What It Does Not — Fact check: is Turkey's defense industry really 80 percent domestic? We test SSB figures against engines, sanctions and SIPRI data. Verdict: partly accurate.
• International Affairs Desk: Export Controls and Embargoes: How Does Ankara Explain Its Argument Over Allied Arms Restrictions and Double Standards? — Desk analysis of Turkey arms export restrictions by NATO allies: CAATSA, the F-35 removal, the 1975–78 embargo, EU rules and Ankara's double-standards case.
• Regionalytic: Fact Check: 'Islands Like Kastellorizo Give Greece Full Maritime Zones and Cut Türkiye Off' — Does Kastellorizo generate full EEZ continental shelf? We test the claim against UNCLOS Article 121, ICJ and arbitral precedents, and Ankara's equity argument.