If murder is not war and war is not murder and we have enemy countrys to kill then because they evil, how do.?

we know our country is not an enemy country and evil if all countries say they are good? If Russia follows the bible and kills all americans in a war because God tells their president to do it, just like God told Bush to do it to Iraq and we all did, then is that okay, cause it not murder as in 'thy shelt not kill' it just war, good countrys against evil countrys. is that right? Is that why war is not murder? Which country are good and which country are evil and how do we really know and at the end of the day are we not talking about killing innocent people. Should not christains follow the Bible or should they follow a flag?