Thirty Years' War
Fifthly, Holy Roman Emperor Matthias, a Catholic, died without any children to take his place in 1619. His lands were given to his cousin Ferdinand of Styria, Matthias's closest male relative, who became Ferdinand II, Holy Roman Emperor. Ferdinand had been educated by the Jesuits. A Catholic, he wanted to make Catholicism the only religion again. That made him unpopular in the German state of Bohemia since most people there were not Catholics but Hussites. The Bohemians rejected Ferdinand and launched the Thirty Years' War.