For spin  and a parameter  for the deformation from the XXX model, the BAE (Bethe ansatz equation) is
Notably, for  these are precisely the BAEs for the six-vertex model, after identifying , where  is the anisotropy parameter of the six-vertex model. This was originally thought to be coincidental until Baxter showed the XXZ Hamiltonian was contained in the algebra generated by the transfer matrix , given exactly by