The War of the Jülich Succession was a war of succession in the United Duchies of Jülich-Cleves-Berg. It lasted between 10 June 1609 and 24 October 1610, resumed in May 1614 and finally ended on 13 October 1614. The first round of the conflict pitted Catholic Archduke Leopold V against the combined forces of the Protestant Margraviate of Brandenburg and Palatinate-Neuburg, ending in the former's military defeat. The representatives of the Brandenburg and Neuburg later entered into a direct conflict after their religious conversion to Calvinism and Catholicism respectively. The conflict was further complicated by the involvement of Spain and the Netherlands making it part of the Eighty Years' War, as well as the European wars of religion. It was finally settled by the Treaty of Xanten, whose provisions favoured Spain. Background The rapid spread of the Lutheran and Calvinist doctrines after the Protestant Reformation was met by a period of Roman Catholic resurgence, known as the Counter-Reformation. Such interdenominational conflicts as the Cologne War and the Strasbourg Bishops' War prompted creation of the Catholic League and the Protestant Union, with the intention of safeguarding the interests of the Holy Roman Empire's Catholic and Protestant nobility, respectively. The aforementioned alliances entered their first conflict in 1609, when a succession crisis in the United Duchies of Jülich-Cleves-Berg sparked the War of the Jülich Succession. The territories in question covered an area of 14,000 km² and had both geopolitical importance from their proximity to the Spanish Road and a booming economy, which was fuelled by refugees fleeing the lands that were being ravaged by the Eighty Years' War. Johann Wilhelm, Duke of Jülich-Cleves-Berg, who was affected by a serious mental illness, died on 25 March 1609 and left no heirs to succeed him. Emperor Rudolf II had claims to the duchies stemming from intermarriage. However, he was unable to declare his intentions openly without compromising his perceived neutrality. A total of six other claimants appeared, with rulers of the Margraviate of Brandenburg and Duchy of Palatinate-Neuburg having the only credible claims through their marriage to Johann Wilhelm's aunts. On 2 April, a regency was established, including the duke's wife, Antoinette of Lorraine; the privy councilors; and an imperial commissioner. On 24 May, Rudolf II announced that the Aulic Council was to provide a definite verdict within four weeks. Conflict Brandenburg and Neuburg viewed the regency as a direct attempt at annexing the