Definition of war of nerves:
(n) :
(idiomatic, by extension) A situation in which opposed parties refrain from direct conflict but maintain a tense, contentious relationship in which each uses annoyances or intimidating psychological tactics to attempt to dishearten and unnerve the other.
(n) :
(idiomatic) Warfare characterized by psychological manipulation, involving tactics intended to demoralize, frighten, and unnerve opponents in order to prompt surrender.