Crimean War: France and Britain declare war on Russia.

The Crimean War (1853–1856) was a major conflict primarily between the Russian Empire and an alliance of the Ottoman Empire, Britain, France, and Sardinia. It was sparked by disputes over the rights of Christian minorities in the Holy Land, then under Ottoman control, but it quickly escalated into a broader struggle for influence in the declining Ottoman Empire. The war is most famous for brutal trench warfare, the disastrous Charge of the Light Brigade, and the pioneering work of Florence Nightingale in modern nursing. Fought largely on the Crimean Peninsula, the conflict exposed serious flaws in military logistics, leadership, and medical care on all sides. It ended with the Treaty of Paris in 1856, which neutralized the Black Sea and forbade Russian naval presence there—temporarily checking Russian expansion. The war marked a turning point in military history, ushering in new technologies like railways and the telegraph, while also highlighting the need for reform in many European armies.