From 1618 to 1648, Europe was engulfed in an interlocked series of brutal conflicts collectively known as the Thirty Years’ War. In basic terms, this extended bloodbath represented a power struggle between the Protestant states of Northern Europe and the Catholic empires of Spain and Austria; at the same time, it constituted a structural contest between an imperial system of governance and the emerging nation-state. Although the fighting did not resolve these struggles in every respect, it did result in a significant shift in power from the southern to the northern states and from imperial to national systems of rule. Indeed, many historians believe that the modern system of nation-states was crystallized in the Treaty of Westphalia of 1648, which finally ended the fighting.