Excerpts from Books and Wikipedia
"The immediate cause involved the rights of Christian minorities in the Holy Land, which was a part of the Ottoman Empire. The French promoted the rights of Roman Catholics, while Russia promoted those of the Eastern Orthodox Church. The longer-term causes involved the decline of the Ottoman Empire and the unwillingness of Britain and France to allow Russia to gain territory and power at Ottoman expense." [Wikipedia] "In 1854, Britain and France decided to assist the Ottoman government and its efforts to defend the Danubian principalities against Russian expansion, and to resist Russia's claims of protection over the Ottomans Christian subjects. An Anglo-French fleet was dispatched to the Crimea. The campaign was largely static, centered on a series of sieges and dogged trench warfare, leading eventually to an Allied victory at the siege of Sebastopol in 1855." [DK Timelines, p. 365] "In Russia the rigid crust of the tsarist autocracy of Nicholas I (1825-55), already under growing strain, cracked. An era of crisis, reform and change began, culminating in the emancipation of the serfs (1861) and the emergence of a Russian revolutionary movement in the late 1860s." [Hobsbawm: Capital, p. 76-7]