Typically, simulations of the combustion of energetic materials have focused on a detailed description of the processes in the gas phase. This is due to an implicit assumption that the burning rate control zone is located in the gas phase at moderate pressures. However, at the present time new arguments in favor of the concept of the condensed phase being the locus of the burning rate control zone for typical energetic materials in "rocket" pressure range have become available. These are based on data of the temperature profiles in the combustion wave of modern energetic materials. Analysis shows that, with pronounced heat release in the condensed phase, self-sustaining combustion can be unstable. This effect may result in the existence of combustion regimes with "cross-surface" combustion waves. The difficulty of formulating a description of the combustion of energetic materials with pronounced condensed phase reactions are discussed.