The causes of the Thirty Years War in Western Europe:

By 1600, two camps had emerged in western Europe:

France and the United Provinces

The House of Habsburg (Spain and Austria)

Phillip III of Spain attempted to continue the foreign policy aspirations of his father, Phillip II, which essentially meant that Spain had to be kept on a war footing.

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.

However, Spain was in a difficult military position. The calamity of the 1588 Spanish Armada defeat had been a shattering blow to Spain’s morale and she had never recovered from this shock. Any Spanish fleet sailing through the English Channel on its way to the United Provinces would never have been tolerated by England. Anti-Catholic feeling was rife in England after the 1605 Gunpowder Plot. Therefore, any military venture by the Spanish would have to be carried out by its army going over mainland Europe – and not by sea.

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.

From the Spanish point of view, the “Road” was a far from safe route. In fact, it left the Spanish army very vulnerable to attack along many parts of it. The route near Franche-Comte and Lorraine were particularly susceptible to attack.

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.

Though the French could not stop the Spanish using the “Spanish Road”, they could hinder its use as in 1601 when France bullied Savoy into giving France land from which she could easily threaten Milan. The reign of Henry IV of France saw many such examples of France hindering the Spanish (though never openly declaring war as she was still suffering from the French Wars of Religion) and the evidence suggests that Spain was so irked by this that both countries were on the verge of open warfare when Henry VI was assassinated in 1610. The minority rule of Louis XIII gave France too many internal issues to concentrate on which temporarily ended the clash with the Spanish. However, both remained very wary of the other. Spain, in particular, feared for her possessions in northern Italy and the Low Countries.

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 Alpine valleys now became a volcano of political, linguistic and religious instability………the area was one of the cross-roads of European politics, where the messengers, troops and treasures of the Habsburg-Catholic axis going one way met those of the anti-Habsburg Protestant axis going the other.”  G Parker


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.

In 1621, the Dutch-Spanish conflict re-started. As was common of the time, those states that could afford to use mercenaries did. The Dutch could afford to do so. To ensure that the focus of the Habsburgs was split, the Dutch encouraged the growing problems in Bohemia where the people of Bohemia were in the process of rising up against their Austrian Habsburg masters. The United Provinces became a focal point of all anti-Habsburg’s feeling.

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.

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