I just want to start by saying that I have found many questions very similar to this one using the search bar, but I still don't understand exactly what happens initially in a simple voltaic cell with a salt bridge (Daniel cell). For example, I am trying to figure out what initially happens in a cell with a zinc anode in zinc sulfate solution connected with an external circuit to a separate jar with a copper cathode in a copper sulfate solution. The salt bridge contains potassium chloride. Because I am concerned about the very beginning of the flow of electrons in the voltaic cell, sources say that the salt bridge does not come into effect yet due to the lack of positive zinc ions. So the charges do not make it through the full circuit yet. Okay, that's fine. So what is the initial reaction that starts this initial one-way flow of charges: zinc is oxidized, copper is reduced, both simultaneously or some other reason?