By Paul Pryce
The Bosporus and Dardanelles Straits, together with the adjoining Marmara Sea, are known collectively as the Turkish Straits and provide the only access between the Black Sea and the Aegean Sea. More than 40,000 vessels passed through these waters in 2019, transporting almost 650 million tons of cargo, and reaffirming the Turkish Straits as one of the most important maritime trade corridors in the world. Additionally, the shores of the Straits – which narrow at some points to as little as 700 meters apart – are home to more than 22 million people, including the historic city of Istanbul.
Since 1936, the Montreux Convention Regarding the Regime of the Straits, hereinafter referred to as the Montreux Convention, has allowed for the peaceful flow of commerce through the Turkish Straits. However, recent calls from Turkish and Russian policy circles for revisions to the Montreux Convention should be cause for concern, as these proposals threaten to either spur a naval arms race in the Black Sea region or look to exploit the Straits as a geostrategic chokepoint.
The Montreux Convention
The Montreux Convention sought to address questions regarding the status of the Turkish Straits that, by the time of the Convention’s writing, had persisted for well over a century, occasionally culminating in violence or near-violence, as in Britain’s effort to wrest control of the Dardanelles in 1922. Among its terms, the Convention stipulates that only littoral states to the Black Sea may transit capital ships (which, if we follow the 1923 Washington Naval Treaty’s definition, refers to “…a vessel of war… whose displacement exceeds 10,000 tons… or which carries a gun with a caliber exceeding 8 inches…”) through the Straits, escorted by no more than two destroyers.
It also prohibits any country from deploying to the Black Sea more than nine naval vessels displacing a total aggregate of 45,000 tons; it requires that no group of non-littoral states deploy to the Black Sea any naval vessel weighing more than 10,000 tons; and it limits the stay of any vessels from non-littoral states to just 21 days. Littoral states are further obliged under the Convention to inform the relevant Turkish authorities of an intended transit of the Straits by a military vessel at least eight days prior and non-littoral states are obliged to provide 15 days’ notice. Turkey is further empowered to close the Straits to all military traffic in wartime or when under threat of aggression while also denying passage to merchant vessels belonging to countries at war with Turkey.
It is worth noting that Annex II of the Convention specifically excludes aircraft carriers from the definition of a capital ship. This does not extend to any other ship transporting aircraft since, at the time of the Convention’s writing, it was not uncommon for battleships and other military vessels to carry observation aircraft. This may explain the Soviet Union’s unusual designation of its aircraft carriers as ‘aircraft-carrying cruisers’ – for example, the Kiev and Kuznetsov classes. These vessels could fulfill the same strategic function as carriers while still being free to transit the Turkish Straits, even as the Convention denied access to the Black Sea for NATO aircraft carriers due to their explicit designation as aircraft carriers in both name and function.
Though the Montreux Convention has constrained the capacity of NATO support to Ukraine in its struggle against Russian aggression, such as by limiting the number of vessels permitted in the Black Sea as part of Standing NATO Maritime Group 2 (SNMG2), the continued implementation of the agreement is in the national interest of the United States and other non-littoral nations. The United States has long supported the “principle of freedom of transit and navigation” referred to in Article 1 of the Convention and, although it has never ratified the United Nations Convention on the Law of the Sea (UNCLOS), the United States already abides by UNCLOS as a matter of customary international law.
On the one hand, this seems to suggest that challenging the legitimacy of the Montreux Convention would advance American interests – after all, the International Court of Justice (ICJ) ruled in 1949 that, for vessels transiting the Straits or Corfu, which runs along the coasts of Albania and Greece and which serves as a passage between the Adriatic and Ionian Seas, the concept of innocent passage should prevail over any claims of state control over such strategic waterways. With the Corfu precedent and the customary nature of UNCLOS, one might assume that a legal challenge of the Montreux Convention by a non-littoral state would easily succeed.
But the unique geography of the Turkish Straits makes this legal question far from simple. The Marmara Sea is an internal sea, all the coasts of which belong to Turkey. In the event of a dissolution of the Convention, the ICJ would need to consider whether the Turkish Straits constitute a single strait connecting two open seas, in which case innocent passage prevails, or if they are two separate straits connecting an open sea and an internal sea, in which case Turkey would be able to exert even greater control over the flow of maritime traffic through the Straits. Referring to the Turkish Straits in common parlance – rather than referring separately to the Dardanelles, the Bosporus, and the Marmara Sea – implies a single unit, and the bulk of the maritime traffic has flowed over the past decade between the Aegean Sea and the Black Sea. It would seem likely then that the ICJ would favor the conception of the Turkish Straits as a single strait connecting two open seas, but this outcome is not guaranteed.
It is also difficult to discern to what extent the United States would be able to practically alter the administration of the Turkish Straits. Turkey is a significant maritime power in its own right and much of its naval forces are stationed at Gölcük Naval Base, located on the east coast of the Marmara Sea. Any freedom of navigation operation (FONOP) would encounter immediate resistance and would add to the existing tensions between the Turkish and U.S. governments, especially as Turkey refuses to recognize UNCLOS.
The economic and social importance of the Straits to Turkey cannot be overstated. Beyond the millions of Turkish citizens who live on its banks and the commerce the Straits facilitate, it also offers a physical representation of Turkey’s duality as a European and Asian state, while the administration of the Straits has afforded Turkey a self-image as the guardian of the Black Sea.
Given all of this, it would possibly require the wholesale destruction of Turkish naval forces to impose a major change in the administration of the Turkish Straits and, even then, barriers could be erected intentionally or accidentally that would interfere with the future use of the waterway. In short, the legal and practical status quo offers the best guarantee for the continued flow of trade through the Straits.
Calls for Reform
However, there has been much discussion in Russian and Turkish policy circles around possible revisions to the Montreux Convention. These revisions would be detrimental to U.S. national interests, which include the maximum possible freedom of transit and navigation through the Turkish Straits. In particular, since the annexation of Crimea, some Russian defense planners have called for the Convention to be revised so that the length of stay in the Black Sea for vessels from non-littoral states would be shorter than the current allowance of 21 days. Furthermore, Russian policymakers have creatively interpreted the Convention since annexing Crimea in 2014.
In May 2016, Turkish President Recep Erdogan decried the Black Sea as a “Russian Lake.” In response, the Chair of the State Duma Committee on Defense, Admiral Vladimir Komoyedov, claimed that the Russian Federation need only inform Turkey of the transit of its military vessels through the Turkish Straits and that restrictions on the number and kind of vessels transiting applied only to non-littoral states. Meanwhile, in response to Russia’s unilateral restrictions on the flow of maritime traffic through the Kerch Strait between the Black Sea and the Sea of Azov, Ukraine called in November 2018 for tighter restrictions on the number and kind of vessels from all states transiting the Turkish Straits, in hopes that this might interfere with the strategic maneuvers of the Russian Navy.
There have been rumblings from the Turkish government as to how Istanbul is “…threatened by the ever growing number of oil tankers and other dangerous cargo vessels” that transit the Straits. While Turkey has been mostly satisfied by regulations adopted through the International Maritime Organization (IMO) and other multilateral bodies, some Turkish commentators have proposed further action. In particular, some suggest promoting a regional ownership model for the Straits under the auspices of the Black Sea Economic Cooperation (BSEC), a multilateral forum comprised of Turkey and the Russian Federation but also Albania, Armenia, Azerbaijan, Bulgaria, Georgia, Greece, Moldova, Romania, Serbia, and Ukraine.
Such a model could facilitate the re-interpretation of the Montreux Convention, loosening the restrictions on vessels from Black Sea littoral states, but maintaining or even tightening the restrictions on vessels from non-littoral states. This could, in turn, be circumvented by the United States and other non-littoral states by re-flagging vessels. In the wake of the Crimean annexation, some American commentators suggested an enhanced NATO presence in the Black Sea by having U.S. Navy ships fly Bulgarian or Romanian flags. But this, too, would likely only add to tensions between the United States and Turkey as well as further undermine the rules-based order.
The Istanbul Canal
A $25-billion infrastructure project announced in 2011 by Turkey’s then-Prime Minister Recep Erdogan, known as the Istanbul Canal, presents the greatest challenge to the legal and practical status quo in the Turkish Straits. The canal would consist of a 45-kilometer waterway bisecting the European side of Istanbul, allowing 160 vessels daily to bypass the Bosporus as they transit between the Marmara and Black Seas. Officially, the Istanbul Canal was proposed to alleviate congestion on the Bosporus and divert tanker traffic toward less sensitive areas of Istanbul. However, Turkish freighter captains have cast doubt on this, noting that the canal as currently envisioned would be too shallow to accommodate many of the tankers Erdogan claims would be diverted from the Bosporus. Indeed, the canal plan calls for a maximum draft of 17 meters.
In reality, the Istanbul Canal may have been introduced to circumvent the Montreux Convention. In January 2018, Turkey’s then-Prime Minister Binali Yıldırım asserted that, as an artificial waterway, the Convention would not apply to the Istanbul Canal and so the Turkish authorities would be able to unilaterally restrict or regulate traffic through it. This again depends on whether the Turkish Straits are understood to be a single unit or as three distinct waterways – the Dardanelles, Marmara, and Bosporus. In the former interpretation, the Convention could still apply to the canal, given that it connects part of the Straits to the open waters of the Black Sea. In the latter interpretation, however, the canal would be an entirely new and distinct feature to which the Convention would indeed not apply.
In any case, the canal presents a serious threat to the spirit of the Convention. On the one hand, Turkey has consistently advanced the narrative that continued use of the Bosporus is unsafe to the natural environment, the millions who live on its banks, and the hundreds of vessels that transit each day, and so unilateral restrictions on maritime traffic through the Bosporus could be justified on the basis that vessels ought to transit the safer canal route. On the other hand, Turkey could upset the balance of power in the Black Sea region by allowing vessels to transit the canal that would have otherwise been denied passage through the Turkish Straits under the Convention. Either scenario would clash with the U.S. policy of seeking the maximum possible freedom of transit and navigation, while also making NATO’s capacity to support members and partners in the Black Sea region contingent on Turkish whims.
Similar concerns regarding Erdogan’s strategic intentions have been expressed in Russia, with some commentators warning that completion of the canal could soon be followed by a Turkish denouncement of the Montreux Convention. Under the Convention’s provisions, a denunciation by any of the signatories would prompt a conference to be held for the purposes of drafting amendments to the existing Convention or an entirely new agreement on the use of the Turkish Straits. For such a conference to be valid, the Convention calls for participation from three-quarters of the “High Contracting Parties” that are littoral states – in other words, five out of six of what is now Ukraine, Romania, Bulgaria, Georgia, Russia, and Turkey.
It is conceivable, then, that a denunciation by Turkey of the Montreux Convention could be followed by a conference to draft a new agreement, held validly without Turkish participation. But it is unlikely Turkey would readily abide by any new agreement that was drafted without its participation, especially when, from the perspective of the Turkish authorities, the Istanbul Canal and the denunciation of the Montreux Convention would afford Turkey full control over access between the Aegean and the Black Seas.
Fortunately, there are diplomatic options available that could preserve the status quo in the Turkish Straits. For example, through the auspices of the Organization for Security and Cooperation in Europe (OSCE) – of which the United States and all the Black Sea littoral states are members – a series of confidence- and security-building mechanisms (CSBMs) could be developed regarding access between the Aegean and the Black Sea. As exemplified by the Vienna Document, an integral document to the work of the OSCE, CSBMs can include annual exchanges of information on the disposition of military forces, base inspections, and the mutual invitation of observers to military exercises, all of which are intended to demonstrate to neighbors that there is no hostile intent behind various military activities in border areas.
The development of a similar document or agreement pertaining to the Turkish Straits could include a commitment from all parties not to interfere in any way with access between the Aegean and the Black Sea, aside from those powers already afforded Turkey under the Montreux Convention, effectively backstopping the Convention but also de facto extending its remit to any artificial waterways that might be established connecting the Aegean and Black Seas.
There is nothing here that would stop Turkey from refusing to abide by these terms at some later date – after all, Russia suspended its participation in the Conventional Forces in Europe (CFE) Treaty, another OSCE-related CSBM, a little over one year before it mounted its 2008 attack on Georgia. But a suspension of Turkish participation in CSBMs related to the Straits would afford an early warning to the U.S., Russia, and other interested parties that a denunciation of the Montreux Convention may be forthcoming.
Even with a Turkish denunciation of the Convention, CSBMs would help to avoid a regional arms race. The continued exchange of information between the other Black Sea littoral states would provide assurance that no one state intends to take advantage of the change in the practical and legal status of the Turkish Straits, such as by securing a side agreement with Turkey that would allow for an increased buildup of naval forces in the Black Sea. The inclusion of some clear punitive measures for state non-compliance in the CSBM could also deter Turkey from unilaterally altering the practical or legal status of the Straits – for example, the imposition of sanctions by all other parties – but this could also make the conclusion of any agreement on the CSBM unlikely. In any case, it would serve Turkey’s national interests to participate in such an arrangement as CSBMs would provide a safety net for all of the concerned parties, helping to avoid any change in the legal or practical status of the Turkish Straits from escalating into armed conflict.
Beyond multilateral agreements and fora, Erdogan must also contend with public opinion at home. The newly elected Mayor of Istanbul, Ekrem İmamoğlu, has expressed strong opposition to the Istanbul Canal project and handily defeated former Prime Minister Binali Yıldırım, a canal proponent and Erdogan ally, despite alleged efforts by the Turkish authorities to skew the election results in Yıldırım’s favor. Calls for a referendum on the canal also bode ill for Erdogan, with polling in December 2019 showing that more than 72 percent of Istanbul residents are opposed to the project. The canal could be sacrificed in hopes of avoiding a showdown with İmamoğlu for the presidency in Turkey’s anticipated 2023 general election.
Given the strategic importance of the Turkish Straits – and the rumblings for reform from Ankara, Moscow, and even Kyiv – the most prudent course for U.S. policymakers would be to ensure open diplomatic channels, both by pursuing commitments from littoral states in multilateral fora like the OSCE, and by maintaining an open dialogue with all Turkish stakeholders on this issue. Neglecting these diplomatic tools would mean surrendering the initiative to the Turkish authorities, who have thus far demonstrated a willingness to erode the legal order that has governed the Turkish Straits for nearly a century whenever it is deemed to serve narrowly defined national interests.
Paul Pryce is the Principal Advisor to the Consul General of Japan in Calgary, and a long-time contributor to the Center for International Maritime Security (CIMSEC). He has previously written as the Senior Research Fellow for the Atlantic Council of Canada’s Maritime Nation Program and earlier served as a Research Fellow with the Organization for Security and Cooperation in Europe (OSCE) Parliamentary Assembly.
Featured Image: Turkish Navy MILGEM corvette transits by the Dur Yolcu Memorial on its way to the Dardanelles (Turkish Ministry of Defense photo)