We’ve come down to it: Tolstoy wants to answer the question, “what force moves peoples?” (Epilogue.2.2.1).
Historians run into problems when they try to answer this question by talking about the guys in charge, because each historian explains each event differently, depending on his loyalties and political beliefs.
Even the historians who try to figure out where leaders’ power comes from get into trouble. Usually they make some kind of circular argument, like that Napoleon was the product of the political situation he found himself in (namely, the French Revolution) and that Napoleon then produced the next political situation (brutal suppression of French Revolutionaries followed by dictatorship). That’s basically a dog chasing its own tail, logic-wise.
This kind of circular reasoning is a problem for every kind of historian, like historians of culture or military historians, for example.