Especially for this film, historians Mikhail Meltyukhov and Mark Solonin have studied piles of archive documents - almost everything available about the so-calles "pre-war" period. Unfortunately, a lot of documents aren't available. A lot of funds are still classified. While the others are open, but a historian can't get all the important documents. Todau they have to approve or disprove many of the deep-rooted myths.