The causes of the Thirty Years War in Western Europe:
By 1600, two camps had emerged in western Europe:
The House of Habsburg (Spain and Austria)
At the end of the Revolt of the Spanish Netherlands, the southern provinces of what had been the Spanish Netherlands (the so-called “Obedient Provinces”) had remained loyal to Spain and had arranged a twelve year truce with the United Provinces (today’s Holland) in 1609 (the northern region of what had been the Spanish Netherlands but had rebelled against Spanish rule) but few believed that Spain would tamely let go of her this valuable area that contained the city of Amsterdam and its lucrative merchant industry.
After her successful campaign against the Spanish, the United Provinces had built up a powerful navy and had established herself as a powerful commercial and colonial power. The most obvious weak overseas colonies the United Provinces could target belonged to Spain. Phillip III and his advisors knew this and it is known from Spanish documentation that as early as 1618, Madrid had decided to renew the war against the United Provinces so that this threat was eradicated. Victory against the United Provinces would also allow Spain to re-occupy the region and gain access to the large sums of money being made in the state.
The only way to do this was to use what the Spanish referred to as the “Spanish Road”. This was a route that took Spanish troops along the border of France to Luxembourg and onto the Obedient Provinces. North Italian states were relatively free of feeling threatened by the Spanish as they were Catholic; south German states were also Catholic and had little to fear from the movement of Spanish troops. France was also Catholic but she did fear any movement along her border of Spanish troops. Rivalry between France and Spain had gone back centuries and many historians believe that despite the fact that both were Catholic, neither had ever invaded the other simply because the Pyrannees impeded any form of large-scale military movement. France, therefore, remained wary of any movement of Spanish troops along her eastern border.
Another area of weakness was that the southern area of the route relied on political stability in the northern Italian states. Any crisis in any of these states would hinder the Spanish use of the “Road”.
For many years, France had been fearful of Habsburg encirclement. Spain was on her southern border and the Spanish Netherlands had been on her north-east border. France had actively helped the rebels during the rebellion despite the religious differences. To the south-east, Genoa and Milan were considered to be a Spanish satellite. With the success of the Dutch rebels, France would not tolerate any attempt by the Spanish to re-assert her authority in the area. The success of the rebels had lessened the fears of the French with regards to Habsburg encirclement.
The three areas considered the most important to stability in northern Italy were Venice, Savoy-Piedmont and the Papal States.
Phillip II and the popes had never had the best of relationships despite their common religion. Phillip had considered himself to be a true catholic but he did not believe that this meant that he had to allow the popes to involve themselves in internal Spanish affairs. The popes also questioned the wisdom of totally relying on Spain as an ally. Some popes had actively courted France. Clement VIII had given Henry IV absolution while Urban VIII had tried to end the influence of the Habsburgs in general – both Spanish and Austrian.
Venice had always been wary of Spanish influence in northern Italy. This rich but small state was essentially surrounded by both Austrian and Spanish Habsburgs and she feared that either would attempt to take over Venice to gain its lucrative trading links. Venice did what it could to curb Spanish influence in Italy.
The real maverick of north Italy was Duke Charles Emmanuel of Savoy-Piedmont. He was so unpredictable that even Madrid did not trust him. Unfortunately for Spain, the “Spanish Road ” passed through his territory. One of the main foreign policy goals of Spain at this time, was for Spain to find an alternate route that by-passed Savoy.
In 1593, Spain had opened up a route called the Valtelline. This went from northern Milan, through the Alps and to Tyrol. The most important area of the Valtelline was owned by a family called the Grisons who were Protestant. The people who lived in the valley were Catholic. They constantly feuded with the Grisons.
In 1602, France had been given permission to use the Valtelline to get to Venice but this permission was withdrawn when the Duke of Milan, fearing an attack by the French, threatened the Grisons with war. In 1609, Charles Emmanuel expelled the Spanish garrison in Savoy and one year later, Savoy and France agreed to attack Lombardy but the assassination of Henry IV ended this.
The area on northern Italy became more unstable with the death of the Duke of Mantua in 1612. He left no obvious heir – a recipe for potential problems. In an effort to prevent Spain taking control, Charles Emmanuel declared himself ruler of Mantua. In response to this, Milan invaded Savoy and Charles was forced to withdraw from Mantua. Charles then forwarded a legal claim to Mantua. Spain determined that Charles should not take over this territory and attacked Savoy. Charles was defeated and had to re-open the “Spanish Road” which he had shut for the duration of the conflict. Despite this apparent defeat, Charles remained a threat to stability.
If the Austrian Habsburg’s called on their Spanish cousins to help them out, Spain could not avoid getting involved in an east European conflict which would involve them moving more troops along the sensitive “Spanish Road”. This would further antagonise the French who would give more and more help to the Dutch. The end result would lead to Europe descending into a war that would tear her apart.