Historians that interpret contrary to popular tastes are branded as revisionists, but are often vindicated a generation or two later. In cultures that permit freedom of speech, history tends to become more balanced the further back one goes. What passes for history as taught in primary and secondary schools is actually not history at all, rather a common cultural narrative for the masses, often with a calculated political objective. It’s not just the victors of wars that get to write the narrative. The version the mass of school children are taught is determined politically. Consider the Texas School Board; the majority of its members admit to right-wing religious bias. Most primary and secondary school history textbooks are edited so as not to offend this board.
All is not lost though. As long as primary source documents are preserved, interpretation of historical events tends to become more balanced a century or so after events happened. Only now, for example, are we beginning to see balanced and fair interpretations of the causes and events of the First World War.
This process is only thwarted when powerful institutions, usually government or religious, seek out and destroy primary source documents that could be interpreted contrary to their “party line”. For example, where is the narrative of the Medes or Old Prussians beyond the fact that they existed? What is the true history of any religion, once orthodox zealots have “purified” the archives?
Another problem that has evolved over the last 40 years is, that although almost everything is saved in some electronic format, these formats become superceded making the material unreadable as retrieval devices are scrapped as obsolete. Also the electronic media is not as permanent as we once thought, tapes and discs degrade over time, faster than paper.