"history that is from the mouth of someone who was present will not be entirely objective, but it generally is the most accurate."

WRONG the person who is present will only "see" the things he "sees" and "know" the things he was "allowed to know" about any particular event. The person who was present will know absolutely nothing of the enemy side of things. Add to that the variance among those who were present and the comparison of what it was they "saw". Ask any policeman and they will tell you that eye-witness testimony is great if you only have one eye-witness - if you have a busload of twenty you get twenty vastly different accounts of what they "saw".