It was supposed to be the war to end all wars. Of course, it was not. Since that time, there have been big and little wars between nations. Many countries still have hatreds between people of different races and religions. Anger causes problems between friends.
Families have arguments.
A war between good and evil is fought in each person's soul. We are at war with each other, with ourselves, and, most of all, with God. The prophet Isaiah tells us to be comforted. Our sins can be forgiven and our warfare ended. A peace treaty between God and man was accomplished by Jesus when He paid the penalty for the sins of the world on the cross.