As far as I know, the German/Russian rivalry is a relatively new phenomenon. So, how could we get it to start up earlier? Is there any realistic POD that would result the medieval Russians going to war against the Holy Roman Empire?
Eh, not really. You can make a pretty valid argument that it started in the early 1240s with the German knightly orders trying to expand their Baltic conquests into Russia in the wake of the Mongol and Swedish invasions.As far as I know, the German/Russian rivalry is a relatively new phenomenon.