The first period of the war was thus favorable to the Habsburg and
Catholic causes. Between 1618 and 1620, revolt had been suppressed in
Bohemia and an influential Rhenish electorate had been transferred from
Calvinist to Catholic hands.
Now, however, the northern Protestant princes took alarm. If they had viewed with composure the failure of Frederick's foolhardy efforts in Bohemia, they beheld with downright dismay the expansion of Bavaria and the destruction of a balance of power long maintained between Catholic and Protestant Germany. And so long as the ill-disciplined remnants of Frederick's armies were behaving like highwaymen, pillaging and burning throughout the Germanics, the emperor declined to consider the grant of any concessions.
[Sidenote: 2. Danish Intervention. Christian IV]
At this critical juncture, while the Protestant princes were wavering between obedience and rebellion, Christian IV of Denmark intervened and precipitated the second period of the war. Christian IV (1588-1648) was impulsive and ambitious: as duke of Holstein he was a member of the Holy Roman Empire and opposed to Habsburg domination; as king of Denmark and Norway he was anxious to extend his influence over the North Sea ports; and as a Lutheran, he sought to champion the rights of his German co-religionists and to help them retain the rich lands which they had appropriated from the Catholic Church. In 1625, therefore, Christian invaded Germany, supported by liberal grants of money from England and by the troops of many of the German princes, both Calvinist and Lutheran.
[Sidenote: Wallenstein]
Against the Danish invasion, Tilly unaided might have had difficulty to stand, but fortune seemed to have raised up a codefender of the imperialist cause in the person of an extraordinary adventurer, Wallenstein. This man had enriched himself enormously out of the recently confiscated estates of rebellious Bohemians, and now, in order to benefit himself still further, he secured permission from the Emperor Ferdinand II to raise an independent army of his own to restore order in the empire and to expel the Danes. By liberal promises of pay and plunder, the soldier of fortune soon recruited an army of some 50,000 men, and what a motley collection it was! Italian, Swiss, Spaniard, German, Pole, Englishman, and Scot,—Protestant was welcomed as heartily as Catholic,—any one who loved adventure or hoped for gain, all united by the single tie of loyalty and devotion to Wallenstein. The force was whipped into shape by the undoubted genius of its commander and at once became an effective machine of war. Yet the perpetual plundering of the land, on which it lived, was a constant source of reproach to the army of Wallenstein.
The campaigning of the second period of the war took place in North Germany. At Lutter, King Christian IV was defeated overwhelmingly by the combined forces of Tilly and Wallenstein, and the Lutheran states were left at the mercy of the Catholic League. Brandenburg openly espoused the imperialist cause and aided Ferdinand's generals in expelling the Danish king from German soil. Only the lack of naval control of the Baltic and North seas prevented the victors from seizing Denmark. The desperation of Christian and the growingly suspicious activity of Sweden resulted in the peace of Lubeck (1629), by which the king of Denmark was left in possession of Jutland, Schleswig, and Holstein, but deprived of the German bishoprics which various members of his family had taken from the Catholic Church.
Following up its successes, the Catholic League prevailed upon the Emperor Ferdinand II in the same year (1629) to sign the Edict of Restitution, restoring to the Church all the property that had been secularized in violation of the peace of Augsburg of 1555. The edict was to be executed by imperial commissioners, all of whom were Catholics, and so well did they do their work that, within three years of the promulgation of the edict, Roman Catholicism in the Germanies had recovered five bishoprics, thirty Hanse towns, and nearly a hundred monasteries, to say nothing of parish churches of which the number can hardly be estimated.
So far, the religious and economic grievances against the Habsburgs had been confined mainly to Calvinists, but now the Lutheran princes were alarmed. The enforcement of the Edict of Restitution against all Protestants alike was the signal for an emphatic protest from Lutherans as well as from Calvinists. A favorable opportunity for intervention seemed to present itself to the foremost Lutheran power—Sweden. Not only were many Protestant princes in Germany in a mood to welcome foreign assistance against the Catholics, but the emperor was less able to resist invasion, since in 1630, yielding to the urgent entreaties of the Catholic League, he dismissed the plundering and ambitious Wallenstein from his service.
The king of Sweden at this time was Gustavus Adolphus (1611-1632), the grandson of that Gustavus Vasa who had established both the independence and the Lutheranism of his country. Gustavus Adolphus was one of the most attractive figures of his age—in the prime of life, tall, fair, and blue-eyed, well educated and versed in seven languages, fond of music and poetry, skilled and daring in war, impetuous, well balanced, and versatile. A rare combination of the idealist and the practical man of affairs, Gustavus Adolphus had dreamed of making Protestant Sweden the leading power in northern Europe and had vigorously set to work to achieve his ends. His determination to encircle the whole Baltic with his own territories—making it literally a Swedish lake—brought him first into conflict with Muscovy, or, as we call it today, Russia. Finland and Esthonia were occupied, and Russia agreed in 1617 to exclusion from the Baltic sea coast. Next a stubborn conflict with Poland (1621-1629) secured for Sweden the province of Livonia and the mouth of the Vistula River. Gustavus then turned his longing eyes to the Baltic coast of northern Germany, at the very time when the Edict of Restitution promised him aggrieved allies in that quarter.