The Collaborative International Dictionary of English v.0.48:

Confederate \Con*fed"er*ate\, v. t. [imp. & p. p.
   Confederated; p. pr. & vb. n. Confederating.]
   To unite in a league or confederacy; to ally.
   [1913 Webster]

         With these the Piercies them confederate. --Daniel.
   [1913 Webster]