Christian IV. of Denmark, who had ascended the throne before the birth of Gustavus, in an inroad upon Sweden, had gained some considerable advantages over the father of that hero. Gustavus Adolphus hastened to put an end to this destructive war, and by prudent sacrifices obtained a peace, in order to turn his arms against the Czar of Muscovy. The questionable fame of a conqueror never tempted him to spend the blood of his subjects in unjust wars; but he never shrunk from a just one. His arms were successful against Russia, and Sweden was augmented by several important provinces on the east. In the meantime, Sigismund of Poland retained against the son the same sentiments of hostility which the father had provoked, and left no artifice untried to shake the allegiance of his subjects, to cool the ardour of his friends, and to embitter his enemies. Neither the great qualities of his rival, nor the repeated proofs of devotion which Sweden gave to her loved monarch, could extinguish in this infatuated prince the foolish hope of regaining his lost throne. All Gustavus's overtures were haughtily rejected. Unwillingly was this really peaceful king involved in a tedious war with Poland, in which the whole of Livonia and Polish Prussia were successively conquered. Though constantly victorious, Gustavus Adolphus was always the first to hold out the hand of peace. This contest between Sweden and Poland falls somewhere about the beginning of the Thirty Years' War in Germany, with which it is in some measure connected. It was enough that Sigismund, himself a Roman Catholic, was disputing the Swedish crown with a Protestant prince, to assure him the active support of Spain and Austria; while a double relationship to the Emperor gave him a still stronger claim to his protection. It was his reliance on this powerful assistance that chiefly encouraged the King of Poland to continue the war, which had hitherto turned out so unfavourably for him, and the courts of Madrid and Vienna failed not to encourage him by high-sounding promises. While Sigismund lost one place after another in Livonia, Courland, and Prussia, he saw his ally in Germany advancing from conquest after conquest to unlimited power. No wonder then if his aversion to peace kept pace with his losses. The vehemence with which he nourished his chimerical hopes blinded him to the artful policy of his confederates, who at his expense were keeping the Swedish hero employed, in order to overturn, without opposition, the liberties of Germany, and then to seize on the exhausted North as an easy conquest. One circumstance which had not been calculated on -- the magnanimity of Gustavus -- overthrew this deceitful policy. An eight years' war in Poland, so far from exhausting the power of Sweden, had only served to mature the military genius of Gustavus, to inure the Swedish army to warfare, and insensibly to perfect that system of tactics by which they were afterwards to perform such wonders in Germany.