Electrical breakdown is generally a progressive wave phenomenon governed by fluid dynamical equations relating mainly to the electron gas. Computer solution of these equations has now been investigated extensively, resulting in improvements in their formulation and in the understanding of the conditions under which solution is possible. In this work the advance of the proforce waves into both neutral and preionized gas has been investigated, and the results are completely satisfactory. Also in this work the advance of the antiforce waves, with and without current, has been investigated and we were able to meet the boundary conditions at the end of the wave within the accuracy of the integration step. The most significant new discovery is the importance of heat conduction and existence of an electron temperature derivative discontinuity at the leading edge of the wave.