I love the quiet and the peace of this liturgy. From the Phos Hilaron to the Magnificat, from Psalm 141 to the great Ektenia litany. Yet it is the Collect of Peace itself which I think expresses the very heart of the vesperal prayer of Christ's Church.
I am always struck by what it doesn't ask. It doesn't ask to be delivered from our enemies. Rather, to be delivered from the fear of our enemies. The peace for which we pray doesn't come from an external fix that would leave us no longer fretting only so long as the external fix held (and no external fix holds for very long in this sad and fallen age). It comes rather from the fretting being removed from our own hearts, so that we no longer fear our enemies (meaning, of course, those who hate us, not vice-versa - we're not given that "luxury").
So as Christians used this prayer in the evening in the days of the Vikings, they admitted it wasn't the terrorist marauding at night and bringing havoc upon them that was the problem; the problem was that their heart would fear that. So they prayed for deliverance from the fear of their enemies so that their hearts could be SET on the obedience to God's commandments: to love all, especially those who mistreat and abuse us, and to trust always in Him whose love for us works...finally, fully, lastly...to our good, for He is indeed a great Lover of Mankind!