Being born into the sin of Adam we are born in a state of warfare with God. However, Christ by His death has opened a way for His people to have peace with God. Those who remain outside of Christ and His salvation remain in a state of enmity or warfare with God, but those who have received Christ in faith are no longer at war with Him.
Christ has not only removed the warfare but has actually brought us into a relationship with God where He calls us His children and we call Him, ‘Father’. This new relationship is one that we can exult and boast in, not because we have done anything to deserve it, but because Christ has brought us to it by His death and resurrection.