What were the motives of the Thirty Years' War?

During the reformation, major violence broke out in 1618 when unhappy Protestants threw two Catholic officials out of a window in the city of Prague. Their action was a response to a new policy issued by the king of Bohemia- a part of the empire. The king had decided to make everyone in his kingdom become Catholic. To enforce his decision, he closed all Protestant churches in Bohemia. The king's decision upset many Protestants. In Prague, unhappy Protestants overthrew their Catholic ruler and replaced him with a Protestant one. Their action did not resolve anything, however. Instead, it added to the religious conflict in the Holy Roman Empire. Their revolt quickly spread into other parts of the empire. This rebellion began what is known as the Thirty Years' War, a long series of wars that involved many of the countries of Europe.