I would guess the erliest would be if either Ukraine surrenders or there is a domestic protest that puts Putin under severe pressure. The latter probably only w

I would guess the erliest would be if either Ukraine surrenders or there is a domestic protest that puts Putin under severe pressure. The latter probably only works if Putin has to step down because I don't see him backing out. Otherwise increasing sanctions to disrupt the supply for the war machine is probably most effective. Don't cut communication lines to Russians, try to get information to them that counteracts state propaganda.