Ocober 24 - 1648 - The Peace of Westphalia
The Thirty Years' War was a nasty, nearly European wide conflict that began as a conflict between Catholicism and Protestantism, but evolved into a much more complicated collision of the great powers of the time. It was so wearing and horrible that when the end of the war was negotiated, the main parties sought a truce that would bring about a new balance of power. Instead, they created a new international order. Put simply, religious toleration was guaranteed across mainland Europe, national borders would be recognized more closely, and the sovereignty of each nation would not be threatened by foreign. These ideas would come to be known as "Westphalian sovereignty" and governed international relations for three hundred years.