Unlawfulness of killing children, Unlawfulness of Killing women and Unlawfulness of Killing elderly person. Prophet
Unlawfulness of Killing Monks and unlawful to destroy their places of worship. Ethics set by Prophet (peace be upon him).
Prophet (peace be upon him) made it unlawful to destroy buildings.
For more ethics on war as taught by the Merciful Prophet (peace be upon him) visit this link.