The Peace of Westphalia constitutes an important epoch in the history of Europe. It marked the close of the struggle in Central and Northern Europe between the Reformation and Counter-reformation movements, and the failure of the attempts of Emperor Ferdinand III to form all Germany into an Austrian and Roman Catholic empire. After the Peace of Westphalia, commercial rather than religious motives regulated the policy of the chief states of Europe. But the peace did not merely mark a revolution in men's ways of thought; it also signalized a remarkable change in the balance of forces on the Continent. For upward of a century the Hapsburgs, supreme in Vienna and Madrid, and closely united by family ties, had threatened to impose their will upon Europe. After 1648 the danger ceased. The weakness of the Emperor and the strength and independence of the German princes rendered any close union with Spain impossible, while Spain herself, though she struggled till 1659 against her impending fate, was already a declining power. From another point of view, the Peace of Westphalia had a special interest. It affords an admirable illustration of a successful effort on the part of the German princes to strengthen their own position at the expense of the central power. All over Europe the monarchical principle was being assailed. In Holland the power of the stadtholder depended entirely on the will of the merchant aristocracy; in England a republic was shortly to be established; in Italy the revolt of Masaniello seemed at one time likely to lead to the formation of a Neapolitan government independent of Spain; and even in Russia aristocratic discontent against the Czar existed. Thus the movement in France against Mazarin, which shortly developed into the Fronde struggle, was but one of many similar manifestations of a general tendency all over Europe to attack monarchical institutions. Mazarin was well aware of the impossibility of checking the general disaffection in France till Austria had been humbled, and therefore he devoted all his efforts to bringing the war to a successful conclusion. The actual congress was not opened at Munster till April 10, 1644, and it was not till the end of 1645 that the negotiations seriously began. The questions to be settled were many and complicated. France and Sweden demanded compensations either in land or money; the Elector of Brandenburg wished to occupy all Pomerania, which the Swedes had seized; the Elector Palatine demanded restoration to his dominions. Then there were innumerable questions dealing with the religious situation, the United Provinces, Italy, Catalonia, Portugal, the constitution of the empire, and the position of the German princes.