You can see the effect by swapping say a 4-star general with a 1-star general. The valor marker on all units changes immediatly. I havn't checked if you can keep your king (and your army) out of harms way by doing so, but I would imagine it was possible.

But again, sometimes the game has a difficulty finding the "real" general when assigning a victory.

This needs testing IMHO

/KotR