France and Britain declare war on Russia during the Crimean War.

Crimean War was fought mainly on the Crimean Peninsula between the Russians and the British, French, and Ottoman Turkish, with support from January 1855 by the army of Sardinia-Piedmont. The war arose from the conflict of great powers in the Middle East and was more directly caused by Russian demands to exercise protection over the Orthodox subjects of the Ottoman sultan. Another major factor was the dispute between Russia and France over the privileges of the Russian Orthodox and Roman Catholic churches in the holy places in Palestine. Supported by Britain, the Turks took a firm stand against the Russians, who occupied the Danubian principalities on the Russo-Turkish border in July 1853.

The war did not settle the relations of the powers in eastern Europe. It did awaken the new Russian emperor Alexander II to the need to overcome Russia’s backwardness in order to compete successfully with the other European powers. A further result of the war was that Austria, having sided with Great Britain and France, lost the support of Russia in central European affairs. Austria became dependent on Britain and France, which failed to support that country, leading to the Austrian defeats in 1859 and 1866 that, in turn, led to the unification of Italy and of Germany.