About the ancient emperors offering prisoners to ancestral halls.

Offering prisoners is a sacrificial ceremony, which means that the emperor declares meritorious deeds to his ancestors and pays homage to them. The time for offering sacrifices to prisoners should require divination. Generally, the prisoners sacrificed after the death of a country will not be members of the royal family, because they should be kind to the royal family, and they will only be given and then killed unless they don't want to stay. It is not necessary to give prisoners, but it is usually after a total victory to show national prestige.