At that time the rules for warfare were based on chivalry. War was the sport of rich noblemen. Sun Tzu refused to see war as a sport. He used Taoist principles and applied them to warfare. In doing this he changed the rules of war. Unlike generals who enjoyed long campaigns, he understood war was serious. Sun Tzu believed that once a war started, the goal was to defeat the enemy. Sun Tzu was unconventional in that he didn't follow the prevailing wisdom of his time. Other generals were simply unprepared for Sun Tzu's tactics.