In the Great Northern War, Sweden and her young absolute king, Charles XII, had to meet a challenge which Swedish statesmen had long envisaged as a possibility but which hitherto, by good luck and good management, had been avoided: a simultaneous attack by a coalition of powers on the Swedish empire east and west. There had never been any false optimism in Stockholm as to the deep-rooted resentment aroused among her neighbours by Sweden's seemingly irresistible expansion since her secession from the Scandinavian Union of the later Middle Ages. The path of that expansion had been defined by strategic and economic necessities as well as by dynastic and religious considerations, but the whole dynamic process of empire-building had been conditioned nearly as much by the general Baltic and European situation, with its political tensions and local power-vacuums, as by Swedish initiatives. To throw off Denmark's stranglehold over Sweden's approaches to the west and to push Denmark out of the Scandinavian peninsula had been constant preoccupations ever since the War of Liberation, in the same way as border unrest, engendering trouble with the Muscovites in the duchy of Finland, had led to the search for a defensible frontier in the north-east. Yet it had been an appeal for help from the dying Order of the Sword—whose territory was coveted by Denmark, Russia and Poland—that had first precipitated Sweden into ventures south of the Gulf of Finland, and the accident of a Polish marriage that had involved her both in Polish affairs and in the internal conflicts of the Holy Roman Empire.