A Spanish mercenary army surprised a band of rebels at the Battle of Oosterweel in the Habsburg Netherlands, beginning the Eighty Years' War.

The Battle of Oosterweel took place on 13 March 1567 near the village of Oosterweel, near Antwerp, in present-day Belgium, and is traditionally seen as the beginning of the Eighty Years' War. A Spanish mercenary army surprised a band of rebels and killed or captured almost all of them.

Habsburg Netherlands were the parts of the Low Countries that were ruled by sovereigns from the House of Habsburg. Their rule began in 1482 and ended for the Northern Netherlands in 1581 and for the Southern Netherlands in 1797. Habsburg rule began with the accession of Philip the Handsome in 1482, when he succeeded his mother Mary of Burgundy of the House of Valois-Burgundy, who was the ruler of the Low Countries. Philip's son and heir Charles, future King of Spain (1516), and the Holy Roman Emperor (1519), was born in the Habsburg Netherlands and made Brussels one of his capitals.

The Eighty Years' War or Dutch Revolt was an armed conflict in the Habsburg Netherlands between disparate groups of rebels and the Spanish government. The causes of the war included the Reformation, centralisation, excessive taxation, and the rights and privileges of the Dutch nobility and cities.