The price of telling lies is the trust of others in a person's word. In this world, we have our soldiers and our word to defend ourselves. The word of a person and his integrity are his entire self here. It is a representation of that person, and it is the only real resource worth trying to maintain at all costs. If a person allows his word to become as expendable as their soldiers are in war, then that person will find himself treated as expendable. Nations can be rebuilt; soldiers can be nursed back to health; however, broken trust is almost always irreparable. Liars will not be trusted to tell the truth because they have a exhibited a pattern of lying in the past. (A shocking revelation, to be sure.)
It's not a matter of 'who says.' It's a matter of who trusts whom. It isn't a moral issue. Forging documents and passing it off as an objective fact will have only a few possible results: no one will believe anything that person says after discovering the falsehood.
Or worse, people will believe the falsehoods to be the absolute truth. That's a very subtle tyranny. It's forcible manipulation of history. If the written record says events happened a certain way and those involved in the events refuse to challenge the written record as a lie (be it by coercion or otherwise), then how can an objective observer come to any conclusion other than that the lies are truth? It's not just revisionism, it's a creating a whole new truth.