“Casus belli” is one of the hundreds of terms Latin has contributed to international law. When pronounced in Turkish exactly as it is written, it takes on a completely different meaning. Unfortunately, some high-profile television hosts and so-called strategy analysts—whose credibility is often self-proclaimed—continue to look for a “spy,” as if they were in a Mike Hammer detective novel.
In Latin, the exact Turkish equivalent of the phrase casus belli is “reason for war.” States use the term casus belli to justify wars they declare or armed conflicts they initiate. In history, the assassination of Archduke Franz Ferdinand in Sarajevo in 1914 was presented by the Austro-Hungarian Empire as the casus belli for the First World War, while Nazi Germany used the border clashes between Germany and Poland in 1939 as the casus belli for the outbreak of the Second World War.
In Türkiye, however, casus belli (*) is a term most frequently heard in the context of Turkish-Greek relations and the extension of territorial waters in the Aegean. Recently, it has resurfaced due to efforts in Greece to block Türkiye’s participation in SAFE (the European Union programme launched to develop its defence industry and enhance its strategic autonomy), and in Türkiye in connection with statements by Greek politicians claiming Greece has the right to extend its territorial waters to 12 nautical miles.
So what is the real nature of this so-called casus belli between Türkiye and Greece? Let’s take a closer look.
Article 3 of the 1982 United Nations Convention on the Law of the Sea—of which Türkiye is not a party—grants coastal states the right to determine their territorial waters up to a maximum of 12 nautical miles. This provision does not prescribe an automatic territorial-sea width for every country. Other articles of the Convention also set out methods to be applied in the event of disputes between states.
When the Greek Parliament approved the Law of the Sea Convention—signed on 10 December 1982—through a three-article law on 1 June 1995, it included the following paragraph, which triggered the casus belli debate:
Ankara responded forcefully to the Greek Parliament’s move one week later. On 8 June 1995, through the Grand National Assembly of Türkiye (TBMM), a clear message was delivered: Athens should not make a miscalculation.
The late Ambassador Deniz Bölükbaşı, who at the time served as Head of the Department of Maritime and Aviation Affairs at the Ministry of Foreign Affairs, states in his book Dışişleri İskelesi that he personally drafted the text submitted to the TBMM. At the 121st session of the 19th legislative term of the TBMM General Assembly on 8 June 1995, the following decision was announced unanimously by all political parties represented in parliament:
“The balance in the Aegean, which is a common sea between Türkiye and Greece, was established by the Lausanne Peace Treaty of 24 July 1923. At that time, the territorial waters of both countries were determined as three nautical miles. Accordingly, areas of the high seas outside national sovereignty constituted 70 percent of the Aegean Sea.
“By extending its territorial waters to six nautical miles on 8 October 1936, Greece brought 43.68 percent—nearly half—of the Aegean under its sovereignty. However, the Turkish territorial waters in the Aegean, which extended to six miles in 1964, cover only about 7 percent of the Aegean. Half of the Aegean remains in the status of high seas.”
“Greece has most recently expressed its intention to extend its territorial waters to 12 miles by making use of certain provisions of the Law of the Sea Convention that were essentially designed for the high seas and oceans. If this were to occur, Greece would place approximately 72 percent of the Aegean Sea under its sovereignty.
“It is inconceivable for Türkiye—a peninsula—to accept a situation that would require access to the world’s seas and oceans to pass through Greek territorial waters. Türkiye has vital interests in the Aegean.
“While the TBMM hopes that the Greek Government will refrain from taking a decision that would disrupt the balance established by Lausanne by extending its territorial waters in the Aegean beyond six miles, in the event of such a possibility, it has decided to grant the Government of the Republic of Türkiye all necessary powers, including those deemed necessary from a military standpoint, to protect and defend our country’s vital interests, and to announce this situation to the Greek and world public with friendly intentions.”
That is the background of the casus belli debate between Türkiye and Greece.
The “mon chéri”s (**) of the Ministry of Foreign Affairs of the “Old Türkiye” left nothing to chance: to ensure that no one could claim ignorance, they had the declaration published as a document of the UN Security Council on 23 June 1995, thereby placing it on the record (A/50/256, S/1995/505).
The decision of the Greek Parliament was both unnecessary and technically flawed.
Instead of approving the Law of the Sea Convention with a single-article law, repeating a right already recorded in Article 3 of the Convention brought Greece nothing other than provoking Türkiye.
According to the Greek Constitution, any change to national borders requires a parliamentary decision; such matters cannot be left to decrees. Indeed, when Greece extended its territorial waters to 12 miles south of the Peloponnese last year, a parliamentary decision was required.
Nowhere in the TBMM declaration of 8 June 1995 do the words “casus belli” or “war” appear; on the contrary, it speaks of friendship. Yet the deterrent effect it created has so far been sufficient to prevent Greece from creating a fait accompli in the Aegean.
Greece constantly claims—implicitly referring to Türkiye—that the threat to its country comes from the east. In doing so, it deceives both the West and its own public and tries to justify its armament under the perception of a “Türkiye threat.” From this perspective, labeling the TBMM declaration as a casus belli serves Greece’s aim of portraying Türkiye as an aggressive country—it plays into its hands.
Paradoxically, in recent days, criticism has increased in both Greece and Türkiye against the governments’ policies in the Aegean. Last week, a special session on foreign policy was held in the Greek Parliament at the proposal of three MPs.
Take a look at the title of the session: “Loss of ground in foreign policy and the Government’s silence on issues concerning national interests.”
During the session, opposition MPs harshly criticized the government for being stuck at six miles, turning a blind eye to Turkish provocations, allowing the “Blue Homeland” doctrine to be included in school curricula in Türkiye, and remaining silent in the face of violations of Greece’s sovereign rights. Prime Minister Kyriakos Mitsotakis’ planned visit to Türkiye in the first half of February, at the invitation of President Tayyip Erdoğan to attend the High-Level Cooperation Council meeting, was also questioned.
In response, Foreign Minister Giorgos Gerapetritis stated that Greece has the right to extend its territorial waters in the Aegean to 12 miles and would exercise this right when conditions are favorable. Prime Minister Mitsotakis and Defense Minister Nikos Dendias later used similar language.
Similarly, a segment in Türkiye accuses the government of leaving Greek officials’ claims unanswered. Some are even floating bright ideas, such as having the TBMM step in again and issue a new declaration.
However, Greece has been using the same rhetoric for 30 years. There is nothing new in the statements of Greek leaders. At a time when Türkiye’s international standing is at a peak, when Trump praises President Erdoğan in almost every other sentence, this period is far from creating the “favorable conditions” Greece seeks to extend its territorial waters to 12 miles. Dragging the TBMM back into the picture for no reason would create the impression that Türkiye lacks self-confidence and would weaken the deterrent effect of the 8 June 1995 declaration.
If a “spy” must be sought, it is in fact the casus belli itself: politicians on both sides who thrive on tension, and segments of the media that provoke them and give them prominence.
(*) When read phonetically in Turkish, casus belli can be understood as ‘the spy is apparent’, since casus means spy and belli means ‘apparent’ in Turkish, which gives the phrase a completely different and misleading meaning.”
(**) The French expression “Mon chéri” or phonetically “monşer” in Turkish, has been used by the conservative and right-wing politicians in Türkiye to snub traditional Turkish diplomats.
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