Jûbê Yagyû: The Secret Doctrine of Ura-Yagyu, or "Hidden Yagyu", states: "Once engaged in battle, fight to win. That is the first and cardinal rule of battle. Suppress all human emotions and compassion. Kill whosoever stands in thy way, even if that be a Kami or Buddha. Only then can one master the essence of the art. Once it is mastered, thou shall fear no one, though even devils may block thy way."