During the war, the Dutch Republic became a world power for a short time (mainly through its naval strength) and experienced a period of unprecedented economical, scientific and cultural growth.
Background to the War
The Dutch provinces did not decide to secede from the Spanish empire all at the same time, and some never did (mainly what is now Belgium).
In 1500 Charles V was born in Ghent. He was raised in the Netherlands. When he abdicated in 1556, his son Philip II of Spain took over. Contrary to his father, Philip was mainly interested in the Spanish side of his empire.
Ca. 1550 Calvinism started becoming prevalent in the Netherlands. In 1566 many Calvinists stormed the churches to destroy the statues and images of Catholic saints ('beeldenstorm' in Dutch), which they felt were heretical.
As a counter measure, Philip II sent the Duke of Alva, nicknamed the Iron Duke, to the Netherlands with an army to dam the Protestant tide.
In 1568, William I of Orange (or William the Silent), stadtholder of the provinces Holland, Zeeland and Utrecht, tried to drive the highly unpopular Alva from Brussels. This he saw not as an act of treason against Philip II, which is reflected in the current day Dutch national anthem, the Wilhelmus, in which the last lines of the first stanza read: 'de koning van Spanje heb ik altijd geëerd' (I have always honoured the king of Spain).
There was very little support for the actions of William and he had to flee.
Alva also introduced an unapproved tax ('tiende penning' in Dutch).
Unions of Atrecht and Utrecht
Prompted by the new Spanish governor Alexander Farnese (Duke of Parma), on January 6 1579 the southern states (mostly now in Belgium) signed the Union of Atrecht, expressing their loyalty to the Spanish king. Over the following ten years he restored the Catholic religion to much of the area.
In response to the Union of Atrecht, William was able to unite the northern protestant states of Holland, Zeeland, Utrecht, Gelderland and the province of Groningen with the signing of the Union of Utrecht later the same month, on January 23, 1579. This union would later (1581) lead to the independence from Spain, forming the United Provinces of the Netherlands (also known as the States General and sometimes the Dutch Republic).
In 1581, the Spanish sent an army to attempt to recapture the United Provinces, with some success, and on July 10 1584, William was assassinated. With the war going against them the United Provinces sought overseas help from France and England even offering them the monarchy of the Netherlands, which both declined. However England, which had been unofficially supporting their cause for years, decided to offer direct military support.
In 1585 Elizabeth I of England signed the Treaty of Nonsuch, under which she sent 5,000 to 6,000 troops and 1000 horse, under the command of Earl of Leicester, to assist. However William's son Maurice of Nassau, soon bypassed the Earl and became captain-general of the armies in 1587, prompting Leicester to return to England. The continued intervention of the English, who were to stay until 1604, was a major reason for launching the Spanish Armada against England the following year.
Under Maurice's leadership, much of the area of the southern states revolted against the Spanish, or was captured by the United Provinces. Spain was hampered by the financial cost resulting from the loss of the Armada and, in 1595, by the declaration of war against Spain by Henri IV of France, and became financially bankrupt the following year, not for the first time.
Under financial and military pressure, in 1598 Philip ceded the southern states of the Netherlands to Archduke Albert of Austria and his wife Isabella, following the conclusion of the Treaty of Vervins with France. This roughly recreated the territories of the Empire of Burgundy.