In the era of the regents and princes there was much war. The Netherlands was at war with the Spanish because they felt that all Dutch people should be Catholic. The Dutch princes wanted to be Calvinist. They also wanted all Dutch people to be Calvinists. But many Dutch were still Catholic and some became Remonstrant. The Dutch princes fought the Remonstrants and imprisoned them. So there was a lot of fighting in this era because of the religion.
The war with Spain was won in 1648. Now the Republic of the Seven United Netherlands was independent. Prince William of Orange had founded this republic in 1588. He led the rebellion against the Spanish. William of Orange was killed by the Catholic Balthazar Gerards during this uprising. Willem's son, Maurits of Nassau, became the leader of the uprising. Maurits died in 1625. His brother, Frederick Hendrik succeeded him as stadholder and captain-general.
The stadholder was the head of the States-General. The States-General was the highest administration of the republic. They made the political decisions. Frederik Hendrik died in 1647. His position as stadholder was now fulfilled by his son William II.
William II now wanted to turn the republic into a monarchy. That meant that the country would be ruled by a king rather than the States-General. William II wanted to be that king. He didn't become king. But he had established a military dictatorship. This meant that the absolute power lay with the army. William II died of smallpox in 1650. He was no older than 24 years and his first son was not yet born. William III, his son, was born eight days after his father's death.
A city-free period was now under way. The people were happy to be freed from the dictatorship. But foreign policy suffered from the absence of a clear leader. England wanted to form one country together with the Netherlands. The Dutch noblemen did not think this was a good idea. This led to the first Anglo-Dutch war in 1652. This war lasted 2 years. The republic lost this war and had to accept the English conditions for the peace. This meant, among other things, that they were no longer allowed to trade with England.
There were many more wars with England. They fought for governance in the Netherlands and for colonies overseas. These wars were mainly fought at sea. Thus it was that Michiel de Ruijter became one of the most important people in Dutch history. He has sunk many English ships.
The French attacked the Netherlands in 1672. The French king Louis XIV was an absolute ruler and wanted to enlarge his territory. England supported him in his fight against the republic. France, however, was much stronger by land than the English were at sea. Overijssel, Gelderland and Utrecht were conquered within 3 weeks. The republic could not finance this war in the long run and had to withdraw.
The advance of the French to Holland could be prevented because stadholder Willem III flooded the area between the Zuiderzee and the rivers. As a result, the Republic survived the attack of 1672, the year that would become known in history as a disaster year. William III saw an opportunity to make alliances with Brandenburg, Spain, and the German emperor. But it was not until 1678 that the peace of Nijmegen could be concluded.