Belgium's independence began with an opera audience spilling into a Brussels riot
On 25 August 1830, people leaving a performance of La muette de Portici, an opera stirring with national feeling, joined crowds looting shops in Brussels. Within weeks Dutch troops had withdrawn, a provisional government had declared independence, and Europe's great powers were drawing a new country onto the map: Belgium.
The kingdom Belgium broke from was itself new. After Napoleon's defeat at Waterloo in 1815, the Congress of Vienna joined the northern Netherlands with the former Austrian Netherlands under the House of Orange-Nassau, a strong buffer against France. The southern provinces were partly compensation for colonies Britain kept, including Ceylon and the Cape.
The union chafed. The south was Catholic, Flemish and Walloon; the north Protestant. Southerners made up 62 percent of the population but held half the seats in the assembly, only one minister in four, and a small share of officer posts. They also had to help carry the north's far larger public debt, 1.25 billion guilders against 100 million. King William I put education under state control, angering Catholics, and made Dutch the only language of the army in 1823 and 1824, alienating French-speaking elites. A language reform imposing Dutch in Flanders was so unpopular, even among Flemish speakers who used their own dialects, that it was scrapped on 4 June 1830. Southern industry, meanwhile, suffered under free trade and cheap British imports.
Unemployment and industrial unrest turned the Brussels riot into a wider uprising, with factories occupied and machines smashed. Troops briefly restored order, but radicals took the lead and began talking of secession. Southern recruits deserted Dutch units in large numbers, the army pulled out, and on 27 September a provisional government declared independence and called a National Congress.
William appealed to the great powers rather than fight on, and the London Conference of 1830 recognised Belgium. Leopold I became king in 1831. William then tried to take the country back in the Ten Days' Campaign, which failed when France intervened. The Netherlands finally accepted the outcome in 1839 by signing the Treaty of London.
Source: Belgian Revolution