One of the most mysterious phenomenon of nature is annihilation/creation of charges. The process of annihilation is intimately connected with the strong EM field because it happens at very short inter charge distances. Likewise creation of charges happens under the impact of very strong fields (collision of relativistic charges). Few estimates of strong EM field are given, and three possible criteria are reviewed that distinguish the strong from the weak one. One in particular is important and it is based on distinguishing quantum and classical effects. Possible basis for describing the phenomenon of annihilation is strict formulation of the field reaction force, because it gives the correct energy balance between radiated energy in dynamics of charges at the expense of their mechanical energy. It is shown in classical dynamics that the latter also includes the energy of the rest mass of the charges.