Under Charles V, Holy Roman Emperor, and King of Spain, the region was part of the Seventeen Provinces of the Netherlands, which also included most of present-day Belgium, Luxembourg, and some land of France and Germany. The Eighty Years' War between the provinces and Spain began in 1568.
In 1579, the northern half of the Seventeen Provinces formed the Union of Utrecht, a treaty in which they promised to support each other in their defense against the Spanish army. The Union of Utrecht is seen as the foundation of the modern Netherlands. In 1581 the northern provinces adopted the Act of Abjuration, the declaration of independence in which the provinces officially deposed Philip II of Spain.
Queen Elizabeth I of England sympathized with the Dutch struggle against the Spanish, and in 1585 she concluded a treaty with the Dutch whereby she promised to send an English army to the Netherlands to aid the Dutch in their war with the Spanish. In December 1585, 7,600 soldiers were sent to the Netherlands from England under the command of Robert Dudley, 1st Earl of Leicester. However, the English army was wasted away in fruitless military campaigns in the Netherlands and had no real effect of helping the Dutch rebellion.
Robert Dudley returned to the Netherlands in November 1586 with another army. However, the result was no better than it had been in 1585. Philip II, the son of Charles V, was not prepared to let them go easily, and war continued until 1648, when Spain under King Philip IV finally recognised the independence of the seven northwestern provinces in the Peace of Münster. Parts of the southern provinces became de facto colonies of the new republican-mercantile empire.