Explanation: The Thirty Years’ War was a snowballing series of events in the early-mid 1600s in Germany that would eventually pull in most of the great powers of Europe. As one might guess, it was over issues of religious tolerance - Catholics and Protestants despising the notion of living together in the same polities, unable to persecute the HERETICS who didn’t follow the TRUE FAITH, and sure that they could get their way by force-of-arms.