Being a series about military conflict, there is plenty of fighting during the wars. The violence is neither excessive nor cruel. There is some blood, plenty of injuries, and the occasional decapitation. People are more so defeated than killed. And the anime replaces any loss of limbs seen in the manga with broken arms / legs.
It starts off initially with weird animation for the battles, but once you get used to it, it is a fantastic series.
The same VA that did Ichigo from Bleach also voices Xin, the main character in Kingdom. His goal is to be China's Greatest General. And the series follows his rise from peasant to 100-man general. Then it's onto Kingdom S2.