Except that there is. But like other evidence of the horrors of WWII that didn't fit the good guy narrative ? say, footage of the effect of the atomic bombs on human beings, which were censored for decades ? the truly modern slaughter of the First World War is known in theory, but rarely seen.
Ernst Friedrich's 1924 polemic War Against War!, which was published in a new edition in March, defy that ease of categorization between the gentleman's statemate and the following war during which civilians were the easiest target.