One of the primary issues Tolstoy deals with in War and Peace is power. He asks, "what force moves peoples?" (Epilogue.2.2.1). Tolstoy's big idea in is that power is not something inherent to any "great man," like Napoleon or Emperor Alexander. Instead, he sees power as the culmination of all the events of the past as their import is collectively imbued into the people who will affect the future. In other words, power is transferred by a fatalistic, predetermined path to the right people at the right time in the right place. Most of it is wielded by people who are far removed from the actual events they issues orders about, while the closer we get to the actual doers, the less power we can see.
Paradoxically, the most powerful people in the book are those who are able to almost completely give up control, like Kutuzov or Pierre.
Power is shown to be fluid and easily transferrable from person to person. Those in close relationships are constantly experiencing power shifts, and it's the capacity to cope with this instability that makes or breaks the relationship.