Jesus has overcome the world, so we can have peace. What does having peace mean? Peace of mind? Peace from worrying about the cares of the world and events that seem to indicate Satan is winning? Perhaps, but I think of the hymn:
It is well with my soul.
Peace of soul. Peace with God. Peace deep down in our souls. A peace that no event can disturb. Islam, Isis, etc. are enemies of God and pure evil. Yet, they will not win. They will fail.
I have said these things to you, that in me you may have peace. In the world you will have tribulation. But take heart; I have overcome the world. –Jesus quoted in John 16