We put forward through both analytical and numerical methods the advantage of using non–slowly-varying envelope-approximation model equations for describing the propagation of few-optical-cycle pulses in transparent media. It is proven that the dynamical model based on the generic modified Korteweg–de Vries sine-Gordon equation retrieves the results reported so far in the literature, and so demonstrating its remarkable mathematical capabilities in describing the physics of few-cycle-pulse optical solitons.