In 1623, a drunkard, whose religious affiliation is unknown, set fire to a Catholic church in Prague. Prague, which had a Protestant majority, was ruled by Phillip III of Austria, who was a Catholic. Phillip demanded that the Czech Parliament Re-Catholocize, and hand over the culprit. The Parliament refused. Phillip sent his army to invade Čechy, the Czech lands.
The Parliament quickly raised an army, and sent it to the border to head off the invasion force. The armies met at Kaplice, a small town in Čechy. The first day of battle, although bloody, was largely indecisive. The Czechs, by the end, seemed to have the upper hand, but it was negligible. By evening, almost 15 000 were dead when the generals returned to the camps. At dawn, the battle lines reformed, but it was apperant that the Czechs, who had had less men to begin with, were severely weakened. By noon the Czechs were forced to fall back. The Czechs retreated to Cesky Krumlov, where they set up a firm defense at the castle. The Austrians arrived, but each attack was repulsed from the well dug-in Czechs, who although outnumbered fought with vigor. That night, after the Austrians had returned to camp, several thousand additional Czechs arrived. The fresh Czech soldiers, before first light, marched the three miles to the Austrian camp, and preceded to slaughter them while they were caught off guard. Of the 50 000 strong Austrian force which invaded, only 30 000 crossed the border back into Austria. The Czechs, meanwhile, lost 15 000 of 35 000 men. Phillip, humiliated by his defeat, was forced to sign a treaty with the Czechs agreeing give the Czech Parliament the right to elect its own king over lands with a Czech majority, from Saxony and Silesia to Vienna.
German Phase or the North German Revolt
The German princes, sensing weakness from the Holy Roman Emperor's defeat in Čechy, revolted against Phillip en masse in 1624. Phillip hurriedly attempted to muster his forces, and moved north to put down the princes. For ten years, the fighting dragged on with no discernible victor. Phillip, with soldiers from Austria, Italy, Spain, and Bavaria, a loyal German state fought the Northern German princes. In 1634, at the battle of Neckersalm, Viktor Stephan, the prince of Brandenburg, was killed. His troops, loyal only to him, refused to take orders from the other princes, and broke formation, retreating back to the camp. The Germans tried to regroup, but a massive gap was created in the front line. Phillip pressed his advantage, and the German line crumbled.
Cardinal Richelieu, de facto ruler of France, seeing an oppurtinity to increase France's power over the Habsburgs, persuaded King Louis XIII to side with the Germans in 1634. The French sent troops into Germany and Italy to fight the Austrians in 1635. They neglected, however, to garrison sufficient troops on the Spanish border to the south. In 1635, the Spanish, under Ferdinand IV, the brother of Phillip III, invaded southern France, and advanced all the way to Lyon. Therefore, in 1636 the French, who had made astonding successes against the Austrians in Germany, were forced to return to France and deal with the Spanish threat. The Spanish were pushed back to the border, but only after considerable loss of life. The Germans, meanwhile, had been given time to regroup, and the Austrians could make no more progress.
The English, seeing an opportinity to gain lands in the Americas, declared war on the French in 1638. The French navy attacked the English navy in the Battle of the Channel in 1639. The battle, although indecisive, cost each side dozens of ships. The English, however, made much better progress overseas, occupying much of the French colonies in the Americas.
Treaty of Paris
For five years the war dragged on until 1644. The English Parliament, facing a shortage of funds at home, decided to arrange a peace with France. They wrote up an agreement, and presented it to the German Princes, Phillip III, Ferdinand IV, and the Louis XIII at Paris in 1644. All sides agreed to the conditions, and signed the treaty. France was forced to hand over the French colony of Canada, but could keep Louisiana. Additionally, the German Princes in North Germany were allowed to formally leave the Holy Roman Empire.