Why did Yahweh tell Moses to treat the Midianites as enemies and attack them?

God told Moses to treat the Midianites as enemies and attack them because they had treated Israel like enemies with their deceitfulness.

How did Yahweh refer to Cozbi, the daughter of a leader in Midian who was killed on the day of the plague?

He referred to Cozbi, the daughter of a leader in Midian who was killed on the day of the plague, as their sister.