What is the lie commonly agreed upon?

When Voltaire said "history is the lie commonly agreed upon," he meant that anything written in a history book could be a lie, but because it is a written document everyone assumes it must be accurate. The truth is our very own history books are written by the winners of every event in the past, do you honestly think the winners are going to bad mouth themselves? For example in ever war you only get the winners perspective, because by the time history is written the losers are dead.