Since the period we are considering coincides with the Thirty Years' War (1618-1648), we naturally find that the record of the Jesuits in Germany is full of life and adventure. Their share in bringing about that disastrous and paralysing struggle cannot be measured by the historian. Now that the world realises the baneful effect of that war and of the Catholic policy of intolerance which led to it, in retarding the development of European civilisation, the Jesuit authorities are not likely ever to publish such documents in their archives as would reveal their activity. We must be guided by two chief considerations. In the first place, the general historian can trace the movements which led to the outbreak of war without any reference to the Jesuits, and is therefore not disposed to think that their intrigues were an essential element in the incitement of it; on the other hand, however, the Jesuits were the most earnest and insistent advocates of the harsh Catholic policy which occasioned the war, and they had considerable influence over the Catholic leaders. Ferdinand II., Maximilian of Bavaria, and Wallenstein had been trained in Jesuit schools; Tilly had actually entered the Society, but withdrawn before he had taken the vows. Jesuits swarmed in the Catholic camp, especially about the tent of Tilly, fired the soldiers to their work, and advanced in the rear of the army to occupy whatever towns fell to their arms.
The war began, it will be remembered, in Bohemia, and here the Jesuits were very clearly interested. When the Protestants cast off the yoke of the Emperor in 1618, they swept the Jesuits from their country and burned some of their colleges. We can very well imagine the plaints of the Jesuits at the courts of Ferdinand and Maximilian, and are not surprised to learn that eighteen Jesuits accompanied Tilly's troops when they came to subdue Bohemia. It was the beginning of the war. Similarly, when Bethlen Gabor took Hungary in 1622, one of his first measures was to expel the Jesuits; and the victorious Swedes had expelled them from Livonia in the preceding year. It is, however, unnecessary here to follow them through the long course of the Thirty Years' War. They retreated and advanced with the soldiers of the Catholic League, died of plague in the camp or fell under the sabres of the heretics, and maintained the struggle to the end with all the energy which non-combatants could exert. There were even occasions, as at the siege of Prague, when they took arms and fought desperately in the van of the Catholic troops. The alliance of France with the Protestants was a bitter disappointment to them, and they were among the few in Europe who profoundly deplored the Peace of Westphalia (1648), which at last gave a just liberty to Protestantism in Germany. The war, as conceived by them, was a costly and lamentable failure.