In 1815 Napoleon was defeated, and the Netherlands became independent again. The rulers of European countries thought it was a good idea to make the Netherlands stronger, to make them able to resist another French invasion. Therefore, Belgium and Luxembourg were added to the Netherlands. William I, the son of stadtholder William V, became king. Some Belgians disliked their Dutch king. In 1830 they revolted. William sent an army. He was much more powerful than the Belgians but after ten days the French sent an army to support them. In 1831 the Belgians chose their own king and Belgium became an independent country.