Athens has signalled it may expand its maritime boundaries, and Ankara isn’t happy about it.

Grounds for War

When outgoing Greek Foreign Minister Nikos Kotzias announced last month that Greece intended to expand its territorial waters from six nautical miles off the coast to 12 nautical miles, it reignited a dispute that had been simmering for decades. It may seem like a minor change at first glance, but Greece has thousands of islands scattered throughout the Aegean and Ionian seas, so expanding its territorial limits will have outsize effects on the region.

According to Kotzias, the first planned extension will be to Greek territory in and along the Ionian Sea – from the island of Othonoi to the island of Antikythera. Then, Greece plans to expand the extension to its east coast, from Antikythera to the Saronic Gulf and then through the Pagasitikos Gulf in the Aegean Sea. This is where it has run into opposition, namely from Turkey, which has major ports along the Aegean and depends on free Mediterranean.

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Turkey has long been at odds with Greece over control of the Aegean, and predictably responded with stern warnings. It summoned Greece’s ambassador to Ankara and released a statement reminding Athens of a 1995 declaration by the Turkish parliament that Greek expansion of territorial boundaries beyond six nautical miles would be considered “casus belli,” or grounds for war. In response, Greece has decided to refer the matter to parliament, instead of passing the change through presidential decree as originally intended.

Greece has argued that it has a right under the United Nations Convention on the Law of the Sea to extend its maritime borders to 12 nautical miles, the maximum allowed by the treaty. (Turkey is one of few countries, along with the U.S., that hasn’t ratified UNCLOS, which has more than 160 signatories.)

Since 1936, however, Greece has claimed sovereignty over only six nautical miles from its shores. (Prior to this time, it had control over only three nautical miles.) Turkey wants to keep it that way, claiming that the Aegean is a special case given the proximity of Greek islands to the Turkish coast. According to the Turks, UNCLOS shouldn’t apply there and the issue must be settled through bilateral talks.

Turkey has effectively drawn a red line in the Aegean Sea, and it’s not hard to understand why. If Greece were to extend its territorial control to 12 nautical miles, it would create a potential chokepoint in Turkey’s access to the Mediterranean, forcing Turkish vessels departing from, say, the Bosporus (arguably Turkey’s most valuable strategic asset) or even Izmir (a major port on the Aegean) to navigate through Greek-controlled waters. The extension would increase Greek jurisdiction over the surface area of the Aegean from 43% to 71%, and reduce international waters from 49% to 19.7%. It would also increase Turkish claims over the sea, from 7.5% to 8.8%, but navigation through these waters could still be hampered for the Turks by its historical adversary, an unacceptable proposition for Ankara. While UNCLOS does allow for “innocent passage” through sovereign territorial waters, there are restrictions. For example, states are prohibited from carrying out military exercises that involve any sort of weapons, and submarines that travel through the waters must remain above the surface. There are also restrictions on loading or unloading any commodities in violation of the laws and regulations of the coastal state and conducting research or survey activities, which Turkey needs to do if it’s to secure access to natural gas supplies in the Eastern Mediterranean.

Enforcement measures for UNCLOS are notoriously weak, but the European Union has backed Greece’s right to extend its territorial control. It’s undoubtedly a worrying development for Turkey, which has increasingly squared off against European countries over drilling rights in the eastern Mediterranean. And if Greece does extend its territorial boundaries, Turkey may not be able to carry out military exercises in these waters to intimidate other countries competing for natural resources there or block European vessels from accessing drilling rigs, at least not without violating UNCLOS, which could draw an EU response.

Extending the maritime boundary by six nautical miles won’t really change much in the balance of power between Greece and Turkey. The balance of power between two states is defined not by what either side says it