The Crimean War was an army war between Russia and an alliance of France, the Ottoman Empire, the UK, and Sardinia that lasted from October 1853 to February 1856. The rights of Christian minority in Palestine, which became part of the Ottoman Empire, were the instant reason for the war. The rights of Roman Catholics were promoted by the French, while those of the Eastern Orthodox Church were promoted by Russia.
Longer-term elements included the Ottoman Empire's fall, the Russian Empire's development at the time of the preceding Russo-Turkish Wars, and the British and French desire to safeguard the Ottoman Empire to maintain the Show of Europe's power balance. It has been commonly observed that the causes, that included a difference over a type in one case, never ever suggested a "bigger confusion of purpose" but instead caused a dispute well-known for its "infamously inexperienced worldwide butchery."
Let's learn more about this often-forgotten war.