Turkey's power over the Black Sea explained

MEE has compiled an explainer on how Turkey's influence over the Black Sea could end up affecting the conflict in Ukraine:

In 1936, world powers including the United Kingdom, the Soviet Union and France agreed in the Swiss town of Montreux that Turkey would control the Bosphorus and Dardenelles as a result of its close proximity to Russia, Ukraine, Romania, Bulgaria and Georgia on the Black Sea.

In addition to control of the straits, the convention gives Turkey power to regulate the transit of naval warships, including closing the straits to all foreign warships during wartime.

Turkey can also deny passage to merchant ships if they are from countries at war with Ankara.

All Black Sea countries, including Russia, Ukraine, Bulgaria, Romania and Georgia, wishing to send vessels through the straits must give Turkey eight days' notice. In comparison, non-Black Sea countries must notify 15 days in advance.
 
However, Black Sea countries can send submarines without prior notice, as long as they have been built, purchased, or sent for repair outside the Black Sea. 

The Turkish government must also authorise aircraft if they cross over the straits. 

Russia-Ukraine war: Turkey's power over the Black Sea explained