  We introduce the first principle model describing frequency comb generation
in a WGM microresonator with the backscattering-induced coupling between the
counter-propagating waves. {Elaborated model provides deep insight and accurate
description of the complex dynamics of nonlinear processes in such systems.} We
analyse the backscattering impact on the splitting and reshaping of the
nonlinear resonances, demonstrate backscattering-induced modulational
instability in the normal dispersion regime and subsequent frequency comb
generation. We present and discuss novel features of the soliton comb dynamics
induced by the backward wave.
