Should we defend ourselves or turn the other cheek?

Is self-defence ever allowed? Or should we always turn the other cheek? And what about war, should we have been passive against fascism? After all we have the example of King David in the bible a man of war and a man after God’s own heart. Self-defence also goes beyond the physical, we are talking about wars of words and of social media. So how do we balance self-defence and pacifism?