Give the Enemy a Ray of Hope - Chinese proverb

The original chinese fable:

In 206 B.C., Cao Cao (155-220), a great statesman, artist of war and man of letters, led his army to attack the city of Huguan. As the city was strategically located and very difficult to access, Cao's army could not take it in spite of great efforts. Cao got extremely outraged and said, "Once I get into the city, I will have all those in it buried alive."

Soon his words were spread throughout the city. As the defenders in the city feared that it would really happen to them, they waged a desperate resistance. As a result, Cao's army found it even harder to win the battle. They made months of attempts to get in but in vain. Cao became more uneasy and consulted with his generals for a scheme.

At a meeting, General Cao Ren rose from his seat and said, "The art of war tells us that we should not put the enemy in too tight a ring that the enemy should be left a way to survive. But now we have been trapping our enemy in a deadly corner. What's more, you have declared to have them all buried alive. This will only make them battle desperately against us, for they would rather fight to death than be buried alive. As I estimate, the enemy has almost run out of supplies. If we now give them a ray of hope by leaving an open in the ring, they are very likely to surrender to us, for they would rather survive than fight to death for nothing."

Cao Cao thought the idea quite sensible and ordered to do as the general said. As had been expected, the defending troops in the city soon crossed over to Cao's side. The city was finally seized without a cruel fight.