Thirty Years' War
The Protestants who had thrown the Catholics out the window created a new Protestant government in Bohemia. Many Protestants in Bohemia and the nearby countries started hating the rest of the Holy Roman Empire. The Holy Roman Empire wanted to stop them from doing so, to fight Bohemia, and borrow Spain's money. However, they thought that if that happened, Bohemia's Protestant friends might come in and start fighting them. That made them try to make an agreement with Bohemia to stop the fighting. However, when Emperor Matthias died in 1619, Bohemia decided not to make the agreement because they thought the Holy Roman government was weak now.