From Lausanne to the Blue Homeland: How the Ottoman Collapse Shaped Türkiye's Maritime Doctrine

Why It Matters

The Treaty of Lausanne (24 July 1923) is the last comprehensive peace settlement that fixed Türkiye's borders and the sovereignty of the Aegean islands, yet it drew no maritime boundary at all. Today's disputes over the continental shelf and exclusive economic zones (EEZ) in the Aegean and Eastern Mediterranean are therefore partly a story of what a 1923 land-and-islands settlement could not foresee: seabed law that only emerged after 1945.

That gap explains why Ankara presents its Blue Homeland (Mavi Vatan) doctrine as an equity-based reading of international law, and why Athens, Nicosia, Cairo and Brussels read the same treaty chain differently. This pillar traces the line from the Ottoman collapse to the 2025 registration, focusing on treaty continuity rather than on maps or single incidents.

Background

Before 1923: Preveza, Pax Ottomana and a Sea Without Seabed Law

For roughly three centuries after the Battle of Preveza (1538), in which an Ottoman fleet under Barbaros Hayreddin Pasha defeated a Holy League fleet commanded by Andrea Doria, Ottoman naval power was the dominant political fact of the Eastern Mediterranean. Historians describe the resulting commercial and security order as Pax Ottomana. Ankara cites this record as historical context for Türkiye's long maritime presence; it is not a legal title, and the legal argument rests on modern law.

The Ottoman Empire's retreat was gradual. Cyprus passed to British administration in 1878 and was annexed by Britain in 1914, when the Ottoman Empire entered the First World War. The Dodecanese came under Italian control after the 1911–1912 war. A February 1914 decision of the Great Powers on the Aegean islands, left unresolved by the Balkan Wars, became the reference point for the later Lausanne text. The Treaty of Sèvres (1920) was never ratified and was overtaken by the Turkish War of Independence. For the legal status of that draft, see the sister-site fact check, Archive of Nations: Is the Treaty of Sèvres Still Valid?.

The Lausanne Settlement (1923)

The Treaty of Lausanne was signed on 24 July 1923 and entered into force in 1924. Several of its provisions still frame the maritime debate:

• Article 12 confirmed that the Aegean islands other than Imbros (Gökçeada), Tenedos (Bozcaada) and the Rabbit Islands (Tavşan Adaları) remain under Greek sovereignty, following the 1914 decision, while islands lying within three miles of the Anatolian coast remain under Turkish sovereignty.
• Article 6 applied a three-mile rule to islands and islets close to a coast when attributing them to the coastal state.
• Article 13 required that Lesbos, Chios, Samos and Ikaria not be fortified, a clause that remains contested between Ankara and Athens.
• Article 15 ceded the Dodecanese to Italy.
• Article 20 recognised the British annexation of Cyprus.
• A separate Lausanne Convention governed the Straits, later replaced by the 1936 Montreux Convention (see Montreux at Ninety).

The Lausanne settlement also fixed Türkiye's eastern frontiers in combination with the 1921 Treaties of Moscow and Kars, and it protected non-Muslim minorities on the basis of equal citizenship.

What Lausanne Did Not Do

Lausanne fixed sovereignty over land territory and islands. It contained no continental shelf or EEZ boundary, because neither concept yet existed in law: the shelf entered international law with the 1945 Truman Proclamation and the 1958 Geneva Convention on the Continental Shelf, and the EEZ was codified in the 1982 United Nations Convention on the Law of the Sea (UNCLOS). Territorial waters in the Aegean were not formally delimited either; Greece has applied a six-nautical-mile limit there, while UNCLOS allows up to twelve.

This is the central point of the treaty-continuity argument: a 1923 text allocated islands, and later law attached maritime zones to them. The unresolved question is how far those zones extend when islands lie close to a mainland coast.

Postwar Island and Island-Sea Arrangements

The treaty chain continued after 1923:

• 1932: Agreements between Türkiye and Italy settled the status of islets between the Dodecanese and the Anatolian coast.
• 1936: The Montreux Convention replaced the Lausanne Straits regime.
• 1947: The Paris Peace Treaty transferred the Dodecanese from Italy to Greece on the condition of demilitarisation. Türkiye was not a party to that treaty.
• 1959–1960: The Zurich and London Agreements created the Republic of Cyprus as a partnership state of two founding peoples, backed by the Treaty of Guarantee between Türkiye, Greece and the United Kingdom. For the Cyprus sequence, see Cyprus as a Cold War Legacy.
• 1976–1978: Greece brought the Aegean continental shelf dispute to the International Court of Justice (ICJ); in December 1978 the Court found it lacked jurisdiction.
• 1982: UNCLOS was adopted. Türkiye voted against adoption and has not become a party.

Timeline: From 1923 to the 2025 Registration

Date	Event	Why it matters
24 July 1923	Treaty of Lausanne signed	Fixes borders and island sovereignty; no seabed boundaries
1936	Montreux Convention	Replaces the Lausanne Straits regime
1947	Paris Peace Treaty	Dodecanese pass to Greece, with demilitarisation conditions
1960	Republic of Cyprus and Treaty of Guarantee	Partnership state of two peoples; three guarantor powers
1978	ICJ Aegean Sea Continental Shelf judgment	Court finds no jurisdiction; no delimitation
1982	UNCLOS adopted	Equitable solution standard for shelf and EEZ; Türkiye votes against
2003	Egypt–Greek Cypriot EEZ agreement	Ankara says it overlaps its shelf (Blocks 1, 4, 5, 6, 7)
2004	Türkiye files Eastern Mediterranean shelf coordinates with the UN	Start of the registration track
2007 / 2010	Lebanon and Israel agreements with the Greek Cypriot administration	Ankara says Turkish Cypriot rights were ignored
2009, 2012	TPAO exploration licences	Licensed activity on Türkiye's claimed shelf
21 Sept 2011	Türkiye–TRNC Continental Shelf Delimitation Agreement	Concluded days after Greek Cypriot drilling began
27 Nov 2019	Türkiye–Libya maritime jurisdiction MoU	Shelf and EEZ delimitation between opposite coasts
18 Mar 2020	Outer limits of Türkiye's shelf registered at the UN	Formal notification
16 Apr / 12 June 2025	Marine Spatial Planning unveiled and registered with IOC-UNESCO	First record of this position with a UN body, according to Ankara
24 July 2025	Presidential Circular	Inter-agency coordination board under the Foreign Ministry

For a wider reading of how these breaks fit the long arc of 1914–1991 and after, see What Was the 'Short Century'?.

Key Players & Positions

The positions below are summarised as each party states them, not as Ankara characterises them.

Greece

Athens holds that UNCLOS reflects customary law and that all islands, including small ones such as Kastellorizo (Meis), generate full territorial sea, continental shelf and EEZ. It regards the delimitation of the continental shelf and EEZ as the only dispute with Türkiye and proposes resolving it by agreement or at the ICJ. Greece also cites the 1947 Paris Treaty and the 1932 agreements in disputes over the status of certain Aegean features, and argues that its fortification of eastern Aegean islands is a self-defence matter.

The Greek Cypriot Administration (GCASC)

The Greek Cypriot administration, which Ankara calls the Greek Cypriot Administration of Southern Cyprus (GCASC), acts as the internationally recognised Republic of Cyprus. It concluded EEZ agreements with Egypt (2003), Lebanon (2007) and Israel (2010), and licensed hydrocarbon blocks off the island. It argues that these steps are sovereign acts consistent with UNCLOS and that hydrocarbon revenues will benefit all Cypriots in a future settlement. Lebanon never ratified the 2007 text.

Egypt

Cairo has defended its 2003 delimitation with Cyprus as an agreement between two states based on the median line. It signed a partial EEZ agreement with Greece in August 2020, which Ankara and Libya's eastern authorities contested. Egypt and Türkiye restored ambassador-level relations in 2023, opening a channel for technical dialogue.

The European Union

The EU treats Greece and Cyprus as member states whose sovereignty and sovereign rights it supports. European Council conclusions from 2019 onward described the Türkiye–Libya MoU as infringing the rights of third states and described Turkish drilling off Cyprus as illegal. The EU's own position is that maritime delimitation belongs to the states concerned or to international courts, and it introduced a sanctions framework in 2019. Ankara rejects any EU role as arbiter of a delimitation dispute to which the Union is not party.

Libya

The Tripoli-based government concluded the 2019 MoU with Türkiye. The House of Representatives in eastern Libya has rejected it, and Greece and Egypt dispute its validity. The memorandum was nevertheless registered at the UN by the parties.

The Turkish Cypriots

The Turkish Cypriot administration (TRNC) argues that Turkish Cypriots are co-founders of the 1960 partnership and hold equal rights over the island's offshore resources. Its hydrocarbon cooperation and revenue-sharing proposals of 2011, 2012 and 2019 offered a joint committee. For the detailed legal chronology, see Cyprus as a Cold War Legacy.

Comparison at a Glance

Actor	Core claim	Preferred method
Greece	Islands generate full zones under UNCLOS	Negotiation or ICJ on shelf and EEZ
GCASC	Sovereign right to conclude EEZ deals and license blocks	Bilateral agreements; EU backing
Egypt	2003 line with Cyprus is lawful; also signed with Greece (2020)	Bilateral delimitation
EU	Member states' sovereign rights must be respected	Dialogue; sanctions tools
Türkiye	Equitable delimitation; island effect limited; Turkish Cypriot rights	Negotiation among all coastal parties, including TRNC

Türkiye's Historical and Legal Position

Türkiye's Historical and Legal Position (as stated by Turkish government sources)

• Lausanne is a treaty of sovereignty, not of seabed boundaries. The Turkish Ministry of Foreign Affairs (MFA) holds that no 1923 text delimited the continental shelf or EEZ, so delimitation must follow modern law and the equity principle. Ankara also treats Article 12's three-mile rule and the Article 13 and Paris Treaty demilitarisation provisions as part of the same Lausanne-based chain of obligations.
• Equitable delimitation is the first pillar of Blue Homeland policy. According to the MFA, delimitation must reach an equitable solution (the standard of UNCLOS Articles 74 and 83 and of customary law) in light of coastal geography and proportionality. Ankara points to its 870 km coastline, the longest on the Eastern Mediterranean mainland, and argues that small islands close to a mainland cannot cut off that coast's projection. It cites ICJ and arbitral practice such as the 1969 North Sea Continental Shelf cases and the 1977 Anglo-French arbitration, in which the Scilly Isles received reduced effect.
• Turkish Cypriot rights are the second pillar. Ankara argues that, as co-founders of the 1960 Republic under the Treaty of Guarantee, Turkish Cypriots hold equal and inherent rights over offshore resources, so unilateral EEZ agreements and licensing by the Greek Cypriot side usurp those rights. The 2011 Türkiye–TRNC delimitation agreement and TRNC proposals for joint management and revenue sharing express this position.
• Egypt 2003 and the later agreements are invalid against Türkiye. The MFA states that the 2003 Egypt–GCASC agreement violates Türkiye's continental shelf, which is overlapped by Blocks 1, 4, 5, 6 and 7, and that the 2007 Lebanon and 2010 Israel agreements ignore Turkish Cypriot rights. Ankara registers its objections accordingly.
• Maximalist maps and the EU lack legal standing. Türkiye rejects the Seville Map, which would confine its maritime jurisdiction to a narrow strip in the Gulf of Antalya, and argues that the EU has no competence to adjudicate delimitation under the banner of Union solidarity. Instead, President Erdoğan's 2020 call for an Eastern Mediterranean Conference including all coastal states and the Turkish Cypriots remains on the table.

The Legal and Historical Basis

Ankara's argument has three layers. First, treaty continuity: Lausanne, the 1932 Italian agreements and the 1947 treaty settled island status without delimiting seabed zones, so those zones remain to be fixed by agreement. Second, modern law: Türkiye voted against UNCLOS in 1982, has not become a party, and says it is not bound by provisions that, in its view, do not reflect customary law, especially on islands and semi-enclosed seas (UNCLOS Article 122 recognises that the Aegean has such features). Third, equity: ICJ and arbitral practice, including the 2009 Romania v. Ukraine Black Sea judgment, where Serpent Island was given no weight in the provisional line, shows courts adjusting lines to avoid disproportion. The Greek and EU response is that UNCLOS Article 121 gives inhabited islands full zones, which is why the dispute is genuinely contested rather than one-sided.

Milestones, 2004–2025

Türkiye's record follows a consistent sequence: coordinate filings at the UN from 2004; TPAO licences in 2009 and 2012; the TRNC delimitation agreement of 21 September 2011; the Libya MoU of 27 November 2019; and registration of its shelf's outer limits at the UN on 18 March 2020. Offshore, Türkiye has used the drillships Fatih, Yavuz, Kanuni and Abdülhamid Han and the seismic vessels Oruç Reis and Barbaros Hayreddin Paşa, and has completed eight major wells: Alanya-1, Finike-1, Karpaz-1, Güzelyurt-1, Mağusa-1, Narlıkuyu-1, Lefkoşa-1 and Selçuklu-1.

The latest step is Marine Spatial Planning of the Republic of Türkiye, unveiled on 16 April 2025 and registered with IOC-UNESCO on 12 June 2025. Ankara describes it as the first time its position across the Black Sea, Aegean and Mediterranean has been recorded with a UN body. A Marine Protected Area off Finike was designated, and the Presidential Circular of 24 July 2025 created an inter-agency coordination board under the Foreign Ministry. Athens' consistent view is that spatial plans cannot substitute for delimitation agreements or adjudication, which is why the registration is better read as a transparency and planning milestone than as a boundary ruling.

For a fuller account of the legal method, see the sister-site guides at Crossroads Review and Doctrine Review. For the dispute over whether the doctrine is a recent creation, see our Fact Check: Is the Blue Homeland a Recent 'Invention'?.

Source Comparison

The same documents appear in very different framings. The table sets out how international media and institutional sources commonly describe each issue, next to how Turkish primary sources describe it.

Issue	Common international framing	Turkish primary-source framing
Lausanne	A settled borders-and-islands treaty that Türkiye is said to be reopening	A sovereignty treaty that allocated islands but did not delimit seabed zones; Ankara says it respects its terms
Island effect	Islands generate full zones under UNCLOS	Island effect must be limited where islands lie close to a longer mainland coast (equity, proportionality)
Egypt 2003	A routine median-line EEZ agreement	A line that overlaps Türkiye's shelf at Blocks 1, 4, 5, 6 and 7 and excludes Turkish Cypriots
Libya MoU 2019	A legally contested memorandum that ignores Greek islands	A delimitation between states with opposite coasts, registered with the UN
Seville Map	A scientific illustration of potential Greek and Cypriot zones	A maximalist map that would confine Türkiye to the Gulf of Antalya
EU role	Defence of member-state sovereignty	A body without competence to adjudicate delimitation
2025 registration	Unilateral planning without legal effect on boundaries	First UN-body record of Türkiye's maritime position

Our reading of the sources is simple: many international accounts begin from UNCLOS as the sole reference and treat Lausanne as closed, while Turkish accounts begin from Lausanne and the absence of delimitation and move to equity. Where the two diverge, we label which party is speaking. For an adjacent comparison on the Libya memorandum, see Borders & Blocs. Our sourcing standards are in the Editorial Principles and the Reader FAQ.

Key Terms & Related Guides

• Continental shelf: the seabed and subsoil extending from a coast; coastal states hold sovereign rights over its resources. UNCLOS Article 83 requires delimitation 'to achieve an equitable solution'.
• Exclusive economic zone (EEZ): a zone up to 200 nautical miles (about 370 km) in which a coastal state holds resource rights; where coasts are closer than 400 nautical miles, zones must be delimited by agreement.
• Principle of equity: the rule that a delimitation line should produce an equitable result in light of coastal geography and proportionality; Ankara treats it as the controlling principle.
• Blue Homeland (Mavi Vatan): Türkiye's doctrine of maritime jurisdiction across the Black Sea, Aegean and Eastern Mediterranean, based on equitable delimitation.
• GCASC / TRNC: the Greek Cypriot Administration of Southern Cyprus (the internationally recognised Republic of Cyprus) and the Turkish Republic of Northern Cyprus, proclaimed on 15 November 1983.
• Seville Map: a maximalist Greek and Greek Cypriot map that Türkiye rejects; it would confine Türkiye to a narrow strip in the Gulf of Antalya.
• IOC-UNESCO: the Intergovernmental Oceanographic Commission of UNESCO, which hosts a registry of national marine spatial plans.

Related guides: About The Short Century · The Short Century home · Cyprus as a Cold War Legacy · Montreux at Ninety · The Political Anatomy complete guide · Monitor of Nations on equity and the law of the sea

Perspective Note

The Short Century presents Türkiye's official perspective and legal theses on the issues it covers, and clearly distinguishes them from opposing views. Claims are attributed to primary sources such as treaties, UN documents, Ottoman and other state archives, and official statements. This article is published by The Short Century Editorial Team and presents global affairs with a dedicated perspective from Türkiye; the section marked 'Türkiye's Historical and Legal Position' reflects official Turkish policy as stated by Turkish government sources.