The Thirty Years' War was a series of wars in Central Europe between 1618 and 1648. It was one of the longest and most destructive conflicts in European history. It was the deadliest European religious war, resulting in eight million casualties. Initially a war between various Protestant and Catholic states in the fragmented Holy Roman Empire, it gradually developed into a more general conflict involving most of the great powers. These states employed relatively large mercenary armies, and the war became less about religion and more of a continuation of the France–Habsburg rivalry for European political pre-eminence. In the 17th century, religious beliefs and practices were a much larger influence on an average European than they are today. During that era, almost everyone was vested on one side of the dispute or another, which was also closely tied to people's ethnicities and loyalties, as religious beliefs affected ideas of the legitimacy of the political status of rulers. The war began when the newly elected Holy Roman Emperor, Ferdinand II, tried to impose religious uniformity on his domains, forcing Roman Catholicism on its peoples. The northern Protestant states, angered by the violation of their rights to choose that had been granted in the Peace of Augsburg, banded together to form the Protestant Union. Ferdinand II was a devout Roman Catholic and relatively intolerant when compared to his predecessor, Rudolf II. His policies were considered strongly pro-Catholic. These events caused widespread fears throughout northern and central Europe, and triggered the Protestant Bohemians living in the dominion of Habsburg Austria to revolt against their nominal ruler, Ferdinand II. They ousted the Habsburgs and elected Frederick V, Elector of the Rhenish Palatinate as their monarch. Frederick took the offer without the support of the union. The southern states, mainly Roman Catholic, were angered by this. Led by Bavaria, these states formed the Catholic League to expel Frederick in support of the Emperor. The Empire soon crushed this perceived rebellion in the Battle of White Mountain, but the Protestant world condemned the Emperor's action. After the atrocities committed in Bohemia, Saxony finally gave its support to the union and decided to fight back. Sweden, at the time a major military power, soon intervened in 1630 under the great general Gustavus Adolphus and started the full-scale great war on the continent. Spain, wishing to finally crush the Dutch rebels in the Netherlands and the Dutch Republic, intervened under the pretext of helping its dynastic Habsburg ally, Austria. No longer able to tolerate the encirclement of two major Habsburg powers on its borders, Catholic France entered the coalition on the side of the Protestants in order to counter the Habsburgs. The Thirty Years' War devastated entire regions, with famine and disease resulting in high mortality in the populations of the German and Italian states, the Crown of Bohemia, and the Southern Netherlands. At the end of the century, after France had invaded the Palatinate again and the area suffered a severe winter, thousands of residents fled as refugees to Protestant England. Many went from there to North America, with passage paid by the Crown in return for a period of work in camps along the Hudson River in New York. Some of these immigrants or their descendants were the first Europeans to be granted land by the English in the Mohawk Valley of New York in 1723 west of Schenectady. Other Palatine Germans settled in Pennsylvania. Both mercenaries and soldiers in fighting armies traditionally looted or extorted tribute to get operating funds, which imposed severe hardships on the inhabitants of occupied territories. The war also bankrupted most of the combatant powers. The Dutch Republic enjoyed contrasting fortune; it ended its revolt against Spain in 1648 and subsequently enjoyed a time of great prosperity and development, known as the Dutch Golden Age, during which it became one of the world's foremost economic and naval powers. The Thirty Years' War ended with the treaties of Osnabrück and Münster, part of the wider Peace of Westphalia. The war altered the previous political order of European powers. The rise of Bourbon France, the curtailing of Habsburg ambition, and the ascendancy of Sweden as a great power created a new balance of power on the continent, with France emerging from the war strengthened and increasingly dominant in the latter part of the 17th century.