It's true that we see history as we read about it and perceive it. Like all the other streams it has different schools of thoughts and historians belonging to these various schools of thoughts present it in their own way. Their prejudices and biases affect their perception.

History is past. You derive it and draw conclusions out of the findings and remains. Human error is unavoidable.

It's good to learn from history. But dwelling in past will block the further process. Use your conscience to do what is the need of hour and make a better impact on future. So that when we go down the pages of history, we have glories to be sung

Till second world war human history is full of violence. It is only the technological developments and their commercialisation which has almost eliminated the need to conquer more land  and slaves. Today economic domination is done without crossing borders. Yet some places war is going on like Syria or Yemen