two Emperors who followed Charles V did not harass the Protestants in any way. His brother, Ferdinand I (1556—1564) strictly kept to the treaties Charles had made, and did his utmost to restore order to Germany. Ferdinand's son, Maximilian II (1564—1576), was a good friend to his Protestant subjects, and did his utmost to keep the peace between Lutherans and Catholics. In his reign the Protestants became divided against each other: they fell into two parties, Lutherans and Calvinists. The Calvinists were followers of John Calvin, a Reformer whose teachings had spread through Switzerland, France, and the Netherlands, and, owing to differences of doctrine, there was the greatest bitterness between the two Protestant bodies.

The excellent Maximilian II was followed by a weak and foolish son, Rudolf II (1576—1612). Rudolf persecuted the Protestants, and ruled so badly that the powerful state of Bohemia rose against him and threw off his rule, his brother Matthias becoming King of Bohemia. The Protestants felt that they stood in great danger and, in 1608, they formed an alliance called the Union. In the next year the Catholics banded together under the name of the Holy League, and from that time the two great parties slowly moved towards a dreadful struggle.

In 1612 Rudolf died and his brother was chosen Emperor. Matthias being now called upon to rule the Empire, he handed over Bohemia to his nephew, the Archduke Ferdinand. The Protestants of Bohemia were very uneasy at this change of rulers, for they knew that Ferdinand was a rigid Catholic and no friend to them. Ferdinand soon showed his feelings by ordering that Protestant churches should be pulled down, and by refusing to listen to any protests on the part of Protestants who had complaints to make.

The proud and fiery Bohemians were filled with anger at this treatment, and the province was ripe for revolt when an act of violence brought about a rupture. A meeting was held in May 1618 at the Palace in Prague: here the Protestant leaders met the governors who ruled for Ferdinand and made anew their complaints of unjust treatment. A dispute arose, and two of the Catholic governors, who were noted for their harshness and injustice, were seized and hurled bodily through a window. From that moment may be dated the Thirty Years' War, a war which was to drag Germany to the lowest depths of misery and suffering.

The Protestants and the Catholics now gathered their forces, and the latter marched into Bohemia in August 1618, only to suffer a defeat. The next March the old Emperor Matthias died and Ferdinand himself was elected Emperor, so that the Protestants knew they had no mercy to expect. The Emperor's army was commanded by a famous soldier, General Tilly, who led the Catholic troops of the League to a great victory at Prague in 1620. This victory crushed Bohemia. The leaders who had risen against Ferdinand were put to death or imprisoned, all Protestant churches were shut up or handed over to the Catholics, the Protestant clergy were slain or banished, and the people were forced to rejoin the Church of Rome or leave the country.

The scene of war now changed to the banks of the Rhine in the province known as the Palatinate. Here the Protestants gained a victory over Tilly in 1622. But the victors were too careless. They divided their forces, and Tilly, rallying his troops anew, fell suddenly on the two scattered foes, and defeated each body in turn in two fierce battles. He was now the master of the Palatinate and he swept it with fire and sword, laying towns and villages in ashes and treating the Protestants, whom he hated, with most savage cruelty.

The Elector of the Palatinate had married the daughter of James I of England, and he had now been driven out of his electorate and outlawed by the Emperor. An alliance was formed to assist him, England, Holland, Denmark, and the Protestant states of North Germany joining to assail Ferdinand. But James I did little for his son-in-law, and Denmark was the only land to give the Protestants any real help.

The Emperor felt uneasy at the prospect of facing a number of enemies and called to his aid Wallenstein, Duke of Friedland, one of the greatest commanders of the day. Wallenstein had gained renown and wealth in the early days of the war in Bohemia, and he came to the aid of Ferdinand at the head of 50,000 men, adventurers from all parts of Europe, who served under his banner in the hope of plunder. In 1625 Wallenstein marched into Saxony and, after overthrowing a Protestant army, made himself master of the province.

The King of Denmark was defeated by Tilly in 1628, and then the two great captains joined their forces and marched into Denmark, and overran it from end to end; at the same time Wallenstein made himself master of the towns along the Baltic coast, and by 1629 the Emperor Ferdinand stood in a position of commanding power in all parts of Germany. He now issued decrees that all Catholic property which had fallen into the hands of Protestants should be restored, that the Protestant form of worship should be suppressed, and that all great Church offices should be filled by Catholic clergy.

The next year, however, saw a great champion of the Protestant cause enter Germany to fight on behalf of his German brethren. This was Gustavus Adolphus, King of Sweden, the "Lion of the North." In 1630 Gustavus landed in Germany with a small army and soon drove away all the Emperor's troops near at hand. As he moved through the country the people gazed upon his progress with wonder. They had fled before the fierce troops of Tilly, or the still more savage adventurers who followed Wallenstein. From this army there was no need to fly. Gustavus Adolphus was the greatest general of his age, and kept his men in perfect order. He allowed no noise or riot in the camp, and morning and evening a religious service was held. He permitted no disorder on the march, and the peasants whose homes had been burned and their barns plundered by the troops of the Emperor, flocked to hail him as their saviour and liberator.

At the first appearance of the small Swedish army the Emperor Ferdinand and his friends in Vienna had been scornful. "We have got another little enemy on hand," jeered Ferdinand, and his courtiers laughed at Gustavus and called him the "Snow King," who would melt away as he came towards the warm south. Before the winter was over their laughter died away. Gustavus proved a "Snow King" in truth, but not in the sense his enemies had meant. It had been the custom of the Emperor's troops to go into winter quarters, and take the field again in the spring, when the fine weather returned. Not so Gustavus. He and his hardy Swedes laughed at frost and snow, and marched and fought in midwinter as gaily as in summer warmth, and during the cold season he made immense progress, seizing town after town and driving the Emperor's men before him.