- immediate cause involved the rights of Christian minorities in the Holy Land, which was controlled by the Ottoman Empire. The French promoted the rights of Catholics, while Russia promoted those of the Eastern Orthodox Christians
- longer-term causes involved the decline of the Ottoman Empire and the unwillingness of the United Kingdom and France to allow Russia to gain territory and power at Ottoman expense
- Nicholas issued an ultimatum that the Orthodox subjects of the Empire be placed under his protection. Britain attempted to mediate, and arranged a compromise that Nicholas agreed to. When the Ottomans demanded changes, Nicholas refused and prepared for war. Having obtained promises of support from France and Britain, the Ottomans officially declared war on Russia in October 1853.
- Frustrated by the wasted effort, and with demands for action from their citizens, the allied force decided to attack the center of Russian strength in the Black Sea at Sevastopol on the Crimean peninsula
- war was officially ended by the Treaty of Paris, signed on 30 March 1856.
- Russia lost the war, and was forbidden from hosting warships in the Black Sea.
- The Ottoman vassal states of Wallachia and Moldavia became largely independent.
- Christians were granted a degree of official equality, and the Orthodox church regained control of the Christian churches in dispute.
-one of the first conflicts to use modern technologies such as explosive naval shells, railways, and telegraphs and one of the first to be documented extensively in written reports and photographs.
- As the legend of the "Charge of the Light Brigade" demonstrates, the war quickly became an iconic symbol of logistical, medical and tactical failures and mismanagement - reaction in the UK was a demand for professionalization, most famously achieved by Florence Nightingale, who gained worldwide attention for pioneering modern nursing while treating the wounded.