Ever since the defeat of Napoleonic France in 1815, it was Russia which was seen to be the greatest threat to peace in Europe, especially by Britain and France. They both knew full well that, since the days of Peter the Great, Russia had ambitions of expanding its influence southwards from the Black Sea into the Mediterranean region.

The block to this ambition was Ottoman Turkey which controlled the Bosphorus and the Dardanelles. As has previously been mentioned, the Ottoman Empire was weak and the so-called "Eastern Question" was basically what would happen when it collapsed.

In 1854, Britain and France became alarmed when Turkey and Russia began to quarrel over who should have authority over the holy places, especially Jerusalem. This argument was a deliberate ploy by Tsar Nicholas I to provoke a war with Turkey which would end, inevitably, in a Russian victory. Russia would then control all of south eastern Europe and the eastern Mediterranean.

Despite frantic diplomatic efforts, Russia and Turkey went to war. No sooner had the war begun than Britain and France joined in, not on the side of Christian Russia, but on the side of Moslem Turkey. For them the Russian threat to British and French control of the Mediterranean could not be tolerated. They intervened primarily to prevent the collapse of Turkey.