The propagation of electron driven shock waves has been investigated by employing a one-dimensional, three-component fluid model. In the fluid model, the basic set of equations consists of equations of conservation of mass, momentum, and energy, plus Poisson's equation. The wave is assumed to be a shock front followed by a dynamical transition region. Following Fowler's (1976) categorization of breakdown waves, the waves propagating into a preionized medium will be referred to as Class II Waves. To describe the breakdown waves, Shelton and Fowler (1968) used the terms proforce and antiforce waves, depending on whether the applied electric field force on electrons was with or against the direction of wave propagation. Breakdown waves, i.e., return strokes of lightning flashes, therefore, will be referred to as Antiforce Class II waves. The shock boundary conditions and Poisson's equation for Antiforce Class II waves are different from those for Antiforce Waves. The use of a newly derived set of boundary conditions and Poisson's equation for Antiforce Class II waves allows for a successful integration of the set of fluid equations through the dynamical transition region. The wave structure, i.e., electric field, electron concentration, electron temperature, and electron velocity, are very sensitive to the ion concentration ahead of the wave.