The Collaborative International Dictionary of English v.0.48:

Unsheathe \Un*sheathe"\, v. t. [1st pref. un- + sheath.]
   To deprive of a sheath; to draw from the sheath or scabbard,
   as a sword.
   [1913 Webster]

   To unsheathe the sword, to make war.
      [1913 Webster]