To preserve these rights was secondary.

The first cause was religion.

The Provinces had been fighting for years against the Inquisition.

Had they not taken arms, the Inquisition would have been established in the Netherlands, and very probably in England, and England might have become in its turn a Province of the Spanish Empire.
The death of William the Silent produced a sudden change in the political arrangements of the liberated Netherlands.

During the year 1583, the United Provinces had elected Francis, Duke of Anjou, to be Duke of Brabant and sovereign of the whole country, under certain constitutional provisions enumerated in articles of solemn compact.