Revolution
Orcs rapidly multiply, and start pillaging countrysides and slowly advance forward.
Though orcs had existed for a long time, their populations, for unknown reasons, suddenly exploded during the First Age. Following this, they were in desperate need to expand their borders, and started violently taking control of other races' territories. In angry retaliation, the Peacekeepers shut down the orcs on all fronts, surprisingly prepared for the uprising. Some historians question whether how this was possible, but regardless of which, the fact remains that the Peacekeepers did their job well.