An army in danger and filled with indignation will certainly be victorious. Ai (哀) here means both pain and anger. These emotions can unite an army and give it extraordinary courage which is very often the deciding factor in battle. In the same way, the side that fights with passion to resist wrongdoing and aggression is filled with justified indignation. Any army fighting a just war is brave and invincible. This concept put emphasis on courage and justice.

When two armies of equal strength fight with each other, the endangered side filled with indignation will be victorious. Laozi