restarting hostilities, Ambrosio Spinola, commander in the Spanish Netherlands, needed to secure the Spanish Road, an overland route connecting Habsburg possessions in Italy to Flanders. This allowed him to move troops and supplies by road, rather than sea where the Dutch navy was dominant; by 1618, the only part not controlled by Spain ran through the Electoral Palatinate. Since Emperor Matthias had no surviving children, in July 1617 Philip III of Spain agreed to support Ferdinand's election as king of Bohemia and Hungary. In return, Ferdinand made concessions to Spain in Northern Italy and Alsace, and agreed to support their offensive against the Dutch. Delivering these commitments required his election as Emperor, which was not guaranteed; one alternative was Maximilian of Bavaria, who opposed the increase of Spanish influence in an area he considered his own, and tried to create a coalition with Saxony and the Palatinate to support his candidacy. A third candidate was the Calvinist Frederick V, Elector Palatine, who succeeded his father in 1610, then in 1613 married Elizabeth Stuart, daughter of James I of England. Four of the electors were Catholic, three Protestant; if this could be changed, it might result in a Protestant Emperor. When Ferdinand was elected king of Bohemia in 1617, he gained control of its electoral vote; however, his conservative Catholicism made him unpopular with the largely Protestant nobility, who were also concerned at the erosion of their rights. In May 1618, these factors combined to bring about the Bohemian Revolt. Phase I: 1618 to 1635 The Bohemian Revolt The Jesuit-educated Ferdinand once claimed he would rather see his lands destroyed than tolerate heresy for a single day. Appointed to rule the Duchy of Styria in 1595, within eighteen months he eliminated Protestantism in what was previously a stronghold of the Reformation. Focused on retaking the Netherlands, the Spanish Habsburgs preferred to avoid antagonising Protestants elsewhere, and recognised the dangers associated with Ferdinand's fervent Catholicism, but supported his claim due to the lack of alternatives. Ferdinand reconfirmed Protestant religious freedoms when elected king of Bohemia in May 1617, but his record in Styria led to the suspicion he was only awaiting a chance to overturn them. These concerns were exacerbated when a series of legal disputes over property were all decided in favour of the Catholic Church. In May 1618, Protestant nobles led by Count Thurn met in Prague Castle with Ferdinand's