My definition of being at peace ( and possibly a lot of other peoples definition too) is that no other country is attacking Britain, and none of our sons/ grandsons are conscripted into battle to fight back.
Islamist terrorists are not the only threat that we may face, or, since we all may not be around for a long time, our children and grandchildren will have to face.Nobody expected Hitler, or what that war entailed.We have to be prepared for anything that comes along in the future, accept a lesser role on the world stage, and as sunseeker says' put your trust in God, and carry a big stick.' Now, if you are a pacifist, you will not use any means to fight, if you accept conventional arms but not nuclear then you will no doubt want unilateral disarmament ( hoping for multilateral is pie in the sky) but there are also a lot of us who wish to keep Trident ( or updated similar).
It's our own point of view, and fortunately the view of all the main political parties to keep Trident.