War between Russia and the allies (Britain, France, Ottoman Turks, joined by Sardinia - Piedmont).
Russian demands for protection of Orthodox subjects of the Ottoman sultan and Russian occupation of Danubian land on the Russo-Turkish border led the Turks to declare war on Oct. 4, 1853.
After the Russian Black Sea fleet destroyed a Turkish squadron, Britain and France entered the war in order to preserve the Turkish sultan as a counterbalance to Russia.
In 1854 the allies landed troops in the Crimean peninsula on the north shore of the Black Sea, and began a siege of the Russian fortress of Sevastopol. The siege lasted over an entire year before the Russians blew up the forts, sank the ships, and evacuated Sevastopol.
The war became notorious for high casualties due to disease and questionable leadership on both sides. Losses amounted to 250 000 men on each side.
Although a peace settlement was worked out in 1856, it did not settle the relations of the big powers in eastern Europe, but it stimulated the Russian czar Alexander II to reform the Russian army in order to compete with the other European powers.