Crimean War
The 1853 to 1856 war that pitted Britain, France, and the Ottomans against Russia and broke the system that had kept Europe calm since 1815.
The Crimean War killed somewhere around half a million people, and it started as an argument over who held the keys to a church in Bethlehem. That was the pretext. The real question was what would happen to the Ottoman Empire as it weakened, and whether Russia would be the one to inherit it. Britain and France decided the answer was no, and for the first time since 1815 the great powers of Europe fought each other.
Russia claimed the right to protect the Orthodox Christians of the Ottoman Empire, which in practice would have given the Tsar a permanent voice inside Ottoman politics. When the Sultan refused, Russia occupied the Danubian principalities in July 1853. The Ottomans declared war in October. In November a Russian squadron destroyed an Ottoman flotilla at Sinop, British newspapers called it a massacre, and Britain and France declared war in March 1854.
The war
Almost all of the fighting happened on one peninsula. The allies landed in the Crimea in September 1854 to take Sevastopol, the base of Russia's Black Sea Fleet, expecting a quick operation. The siege lasted 349 days. Around it were the battles that entered British folklore: the Alma, then Balaclava in October 1854, where the Light Brigade charged the wrong guns after a garbled order and was cut to pieces, then Inkerman in November, fought in fog by units that had lost contact with their own commanders.
Nobody involved was competent. Supplies rotted in Balaclava harbor while the army froze on the heights above it. British troops spent the winter without winter clothing. Of roughly 21,000 British dead, about three-quarters died of cholera, dysentery, and exposure rather than of enemy fire. The Russians, fighting on their own soil, were worse off, because there was no railway south of Moscow and their reinforcements had to walk.
The first modern war
Three things happened here for the first time. The telegraph reached the theater, so London could send orders in hours instead of weeks, and reporters could file just as fast. William Howard Russell of The Times described the condition of the army in print, and his reporting helped bring down the government in January 1855. Roger Fenton photographed the war, though under instructions that kept the dead out of the frame. And Florence Nightingale reached the barracks hospital at Scutari in November 1854 and found men dying of infection faster than of wounds. Her lasting contribution came afterward, when she used statistics to prove to a royal commission that sanitation, not battle, had killed most of the British army.
Nicholas I died in March 1855 and his son Alexander II wanted out. The Treaty of Paris of March 1856 neutralized the Black Sea, banning Russian warships and naval arsenals from it, and stripped Russia of its claim over Ottoman Christians. Russia repudiated the Black Sea clauses in 1870, the moment France was busy losing to Prussia.
What it broke
The war destroyed the arrangement that had kept general war out of Europe since 1815. Austria owed its survival in 1849 to Russian troops, and then stayed neutral in 1854 and mobilized against Russia anyway to force it out of the Danube provinces. Russia never forgave it. Austria was left with no friends at all, and lost to France in 1859 and to Prussia in 1866 with nobody coming to help. Within fifteen years of the Treaty of Paris, Italy and Germany had both been unified by war.
Russia drew a different lesson. It had been beaten on its own territory by expeditionary armies shipped in from a thousand miles away, because it had no railways, obsolete muskets, and an army of serfs. Alexander II abolished serfdom in 1861 largely for that reason.
The question that started it was left open. Who inherits the Ottoman lands stayed the central problem of European diplomacy, through the Congress of Berlin in 1878, the Balkan wars, and Sarajevo.