Source : Webster's Revised Unabridged Dictionary (1913)

Warpath \War"path`\, n.
   The route taken by a party of Indians going on a warlike
   expedition. --Schoolcraft.

   {On the warpath}, on a hostile expedition; hence,
      colloquially, about to attack a person or measure.

Source : WordNet®

warpath
     n 1: hostile or belligerent mood; "the chief is on the warpath
          today"
     2: a course leading to warfare or battle