Strait Talk: Turkey’s Unexpected Influence Over the Crimean Crisis

By: Jessica Caplin and Richard Weir

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As of 8 March 2014, USS Truxtun, a US Navy destroyer, had crossed Turkey’s Bosphorus Strait and entered the Black Sea. Although the US Navy called the mission routine and unrelated to the crisis, tensions in the region between Russia and both the United States and NATO allies have increased in response to the crisis currently embroiling Ukraine and Russia over Crimea. Since the removal of Ukraine’s president on 22 February 2014, the Russian Parliament has focused its attention on this region of Ukraine, approving President Vladimir Putin’s 1 March request to deploy Russian troops into Crimea. Significantly, however, an international convention from 1936 prevents non-Black sea state vessels of war from entering the Strait and remaining in the Black Sea indefinitely and indiscriminately. Under the Montreux Convention of 1936, the USS Truxtun has twenty-one days before it must leave or face violation of international law.

Terms of the Convention

The Montreux Convention of 1936 grants Turkey full power to control access to the Bosphorus and Dardanelles straits.  Under the original terms of the convention, Turkey had authorization to close the Straits to all foreign vessels of war during times of war in which Turkey was a belligerent or when threatened by “imminent danger of war.”  Since Turkey could determine for itself whether or not it was “threatened,” this clause lent Ankara considerable power to control access to Straits.  After Turkey adopted the Straits Regulation in 1982, this power to close the Straits at Ankara’s discretion was expanded to peacetime, as well.

While the Bosphorus Strait is open, several restrictions apply for vessels of war belonging to nations that do not border the Black Sea.  Each individual ship transiting through the Strait must weigh under 15,000 tons.  There can be no more than nine non-Black Sea state warships passing through the Strait at any one time.  The aggregate tonnage of all non-Black Sea state vessels of war in the Black Sea must be less than 30,000 tons.  Thus, if one US vessel of war weighing just under 15,000 tons is already in the Black Sea, all other vessels of war from all non-Black sea states must weigh an aggregate of less than 30,000 tons in order to enter.  Additionally, irrespective of total tonnage of these vessels of war, the convention specifically notes that no submarines or aircraft carriers from non-Black Sea states may enter theSstrait.  Finally, once a ship has entered the Black Sea, it is only permitted to stay for not longer than twenty-one days.  Vessels of war entering the Straits  thus required to notify Ankara several days in advance in order for Turkey to keep watch over these vessels as they enter and exit.

Within the context of the current crisis, Turkey is likely to enforce the terms of the convention, while remaining largely neutral, much like it behaved during the 2008 crisis between Russia and Georgia.  During that crisis, Turkey’s government played a careful balancing act with Russia and NATO allies.  Ultimately, Turkey did facilitate US naval and air movements into the Black Sea and the Caucasus, but it demanded full coordination in advance of US or NATO movement and expressed its desire to avoid confrontation with Russia.  Turkey’s hesitancy stemmed largely from a historic reticence to confront the Russians, as well as its dependence on Russia for roughly fifty-five percent of its natural gas and twelve percent of its oil.

In the current crisis, this measured approach toward Russia will likely rest on the same concerns of energy dependence.  It will be further bolstered by the existence a large Crimean Tatar diaspora in Turkey, which is a Turkic ethnic group in Eastern Europe and Northern Asia. This diaspora, numbering in the millions, will likely demand strong Turkish opposition to Russia in the event Russian forces kill Tatars remaining in Crimea, and Anakara will be forced to balance the demands of both NATO and Turkey’s own population on the one hand with demands of Russia on the other. As a result of this diplomatic balancing, Turkey is likely to stand firm in its execution of the Montreux Convention, demonstrating its respect for an international convention to which Russia is also a signatory.  Such efforts are most likely to help Turkey avoid becoming embroiled in the Crimean conflict while facilitating NATO efforts to deescalate hostilities.

Implications for the United States and NATO

Tonnage restrictions for non-Black Sea vessels of war during times of peace, set at 15,000 for one vessel and 30,000 in the aggregate, severely limit the ability of other nations to come to Ukraine’s aid or to provide a significant show of force in the Black Sea. Indeed, Article 10 of the convention specifically limits the types of vessels, in times of peace, to “light surface vessels, minor war vessels and auxiliary vessels,” regardless of whether they are operated under a Black Sea or non-Black Sea flag. Although modern vessels of war posses a greater capability to inflict damage relative to their size, the tonnage restrictions prevent large ships carrying significant numbers of troops and aircraft from entering the Straits. Thus, while these restrictions allow non-Black Sea countries to place vessels capable of delivering precision strikes, they restrict the same from being able to launch significant military operations from those vessels.

Practically speaking, 15,000 tons is small for a vessel of war. According the US Navy, the standard weight for the largest class of aircraft carriers in the US fleet is around 100,000 tons. Aircraft carriers of this size carry approximately eighty aircraft, many of which are attack aircraft. Vessels of war that are designed and deployed specifically, but not exclusively, by the United States to respond to crises where ground troops could be necessary often exceed the tonnage limitations. For example, US Marine Expeditionary Units, which are a conglomeration of Naval and ground forces deployed together in order to respond to a variety of crises, deploy in a three-ship group. The ships often include one larger vessel, which is capable alone of launching ground forces and airstrikes, and two smaller vessels which are capable of launching helicopters and smaller contingents of ground forces. The larger vessels often referred to as “Amphibious Assault Ships,” weigh in excess of 39,000 tons. The smaller vessels, either an “Amphibious Transport Dock” or a “Dock Landing Ship,” weigh in excess of 17,000 tons. Given the restrictions on tonnage set forth in the convention, none of these types of vessels could enter the Straits. While this restriction seriously constrains US and NATO’s options, it does not eliminate all of them.

Standard tonnage for US Cruisers and Destroyers, both of which are capable of launching guided missile strikes, is around 10,000 tons. This means that, with the permission of Turkey, non-Black Sea countries could place as many as three of these types of vessels in the Black Sea at any given time. Three vessels of this nature would likely be an imposing specter for any country, but these ships can only remain in the Black Sea for twenty-one days at a time. This makes providing a credible threat difficult unless non-Black Sea countries (read: NATO) places ships on a continuous and rigorous schedule of transiting the straits and loitering in the Black Sea, with Turkey’s permission. This would undoubtedly be difficult to coordinate and will likely decrease NATO’s ability to present a credible threat to the Russian government and any attempts it might make to assert control over Crimea.


The Montreux Convention of 1936 has significant implications for the current crisis in Crimea. The United States and its NATO allies, wishing to put pressure on Russia while it tries to exert its influence and “protect its interest” in Crimea, must work within the bounds of the convention. If the situation escalates further, the United States and its allies will be increasingly constrained by the convention and its tonnage restrictions from resorting to traditional methods of exerting pressure. Absent the ability to use these traditional methods, diplomatic channels will become ever more vital as the United States and its allies seek to maintain pressure on the Russian government and show their support for the newly minted Ukrainian government.