  This is the second in a series of papers about torsion-free groups which act
properly and cocompactly on a CAT(0) metric space with isolated flats and
relatively thin triangles. Our approach is to adapt the methods of Sela and
others for word-hyperbolic groups to this context of non-positive curvature.
  The main result in this paper is that (under certain technical hypotheses)
such a group as above is Hopfian. This (mostly) answers a question of Sela.
