The envoys of the Scythians, on being introduced into the presence of the kings of these nations, who were assembled to deliberate, made it known to them that the Persian, after subduing the whole of the other continent, had thrown a bridge over the strait of the Bosphorus, and crossed into the continent of Europe, where he had reduced the Thracians, and was now making a bridge over the lster, his aim being to bring under his sway all Europe also. - Herodotus, The Histories, Book, 450-420 B.C. 
 

Such a position would enable Russia to hold in her hands the keys to Europe and Asia and must be regarded as one of the most disastrous events that could happen. The Black Sea, the Caspian and the Baltic would then indeed become Russian lakes; the Danube, that fine outlet of Central Europe, entirely her own; while with the Adriatic on one side, the Aegean, the Dardanelles and the Mediterranean on the other with an accession to her strength of millions of the most warlike races in the world, she might indeed dictate laws to half the world. - Captain Edmond Spencer, participant in the Crimean War, 1853-1856 - Turkey, Russia, The Black Sea, and Circassia, 1855 

Crimea, which, by its natural ports, by its fortresses from the most ancient times, by the advanced maritime bastion it represents in the Black Sea is obviously in a commanding position over the whole maritime complex here. Whoever owns Crimea can own the Black Sea. - Gheorghe Bratianu, The Black Sea Question, 1943