The Eighty Years’ War was an off-and-on war lasting from 1566-1609, and then from 1619-1648.
It all started when Charles I of Spain and the Holy Roman Empire abdicated, assigning Spain to his son Philip II and the empire to his brother, Ferdinand. Philip ruled the Netherlands and the Habsburg Empire with an iron fist, and the Netherlands revolted under the leadership of William of Orange, launching the Eighty Years’ War. The war was also caused by religious differences: Spain was Catholic, and the Netherlands were Protestant. By 1579, the previously-divided Netherlands had united against Spain, and soon other nations joined the war. In 1609, a twelve-year truce was agreed to.
In 1619, the war resurfaced with the revolt of Bohemia against the Holy Roman Emperor, Ferdinand. Frederick V of the Palatinate was declared king, but the Bohemian rebels were soon scattered, allowing Ferdinand to shift his army towards Frederick’s country. The Dutch Republic was soon under siege, but the Spanish had overextended themselves, and the Dutch broke the siege and continued harassing Spanish treasure ships. Sweden by now had also joined the war, on the side of the Netherlands, and in 1632 its brave king, Gustavus Adolphus, died in battle fighting the Imperial commander, Wallenstein. In 1635, France joined the Netherlands, Sweden, and the German States in the war against the powerful Habsburg Empire. The Netherlands by now had the advantage of having the strongest navy in the world. In 1648, exhausted by the war, both sides agreed to the Peace of Westphalia, with Spain recognizing the Netherland’s independence.
The Eighty Years’ War involved basically all of Europe, and was fought for both political and religious reasons. It exhausted both sides, and resulted in the Netherlands’ independence from Spain.
The Eighty Years’ War proved that even the smallest country, fighting with its allies for independence, could break the power of the largest empire on Earth.