Documentaries are generally about historical facts, but some documentaries may not be like this. This mainly depends on whether the documentary director has done his homework. In other words, have you done your homework on historical materials? This should be a very important aspect, otherwise the documentary may become a TV series or a movie. The most important thing is to pursue the truth. This should be one of the most important requirements of documentary, and there is nothing else to do, that is, this aspect.