Turkey is emerging as a pivotal country in the Ukraine War. As the fighting on land grinds to a bloody stalemate, the importance of naval power has dramatically increased.

As far as Ukraine and Russia are concerned this means the Black Sea and the Bosphorus and Dardanelles that links the sea to the wider world.  Turkey has control over these straits through a series of conventions dating back to the early 19^th century.

Unsurprisingly, President Recep Tayyip Erdogan, is using his position to extract every possible concession from the Russians, Ukrainians and NATO.

At the start of the war the naval balance weighed heavily in Russia’s favour. The Ukrainians had one warship stuck in the repair yard. Moscow, on the other had its Crimea-based Black Sea fleet of 40 surface ships and seven submarines.

Putin used his naval superiority to good advantage. A successful amphibious landing was staged at Mariupol and the Sea of Azov and Kerch Straits were closed to Ukrainian shipping. Odessa and other southern Ukrainian ports were effectively closed by a Russian blockade, bombardment and minefield.

Then the Ukrainians hit back with shore to ship missiles and drones. The first major victim was the fleet flagship, the cruiser Moskva. Then the bridge connecting Russia to Crimea was bombed and now Russian naval installations on Crimea are under bombardment.

Putin badly needs to reinforce his Black Sea naval forces with ships from the Pacific, Baltic and Mediterranean commands. But he can’t. And the reason for this takes us back to the 19^th  and early 20^th centuries and Moscow’s perennially unsuccessful efforts to gain control of the Dardanelles and Bosporus.

Moscow’s first attempt came in the aftermath of the 1828-29 Russo-Turkish War in which the rising Russian Empire defeated the declining Ottoman Empire. As part of the price of victory, Tsar Nicholas I demanded that the straits be closed to all non-Black Sea states.

This would have left the Russian navy in de facto control of the Black Sea which includes all the shipping from the Danube River basin and the northern coast of Turkey. It would also have provided them with their long-sought warm water access. Stalin made a similar attempt at the start of World War II the Cold War.

In the 20^th century Russian pressure led to the Truman Doctrine and Turkish membership of NATO. In the 19^th century the Turks appealed to the West European powers for diplomatic support. The result was the 1841 London Straits Convention in which Britain, France and Prussia pressured Russia into to accepting that only Turkish military ships could traverse the straits in peacetime. This convention was reaffirmed by Russia’s defeat in the 1853-56 Crimean War at the hands of Britain, France and the Ottomans.

The bones of the 1841 treaty are still in effect and have been added to by 1936 Montreux Convention. This guarantees the free passage of civilian shipping but limits the size of warships allowed through the straits and how long they are allowed to stay in the Black Sea. Responsibility for implementing the various treaties lies with Turkey. If Turkey is not at war then it has the right to block the passage of any ships at war. If it is at war then it can take any action that it deems necessary. On February 28, 2022 – six days after the Russian invasion of Ukraine – Turkey closed the Dardanelles to all warships.

Turkey is using its role as geostrategic policeman to extract concessions from all sides. It is saving billions by withholding payments on Russian gas. It has also ignored NATO sanctions to double its trade with Russia in one year. At the same time, Turkey’s clout within the alliance has increased because of its treaty power to treat the Dardanelles as it “sees fit” if it came to a NATO-Russian conflict.

* Tom Arms is foreign editor of Liberal Democrat Voice and author of “The Encyclopaedia of the Cold War” and “America Made in Britain".