What genre do authors generally use to depict historical events?
Probably historical fiction, but could be some others.
Historical fiction is just realistic fiction set in the past. (For example, The Book Thief by Markus Zusak, about World War II.) If the author intends to give some larger meaning to the event or pass some sort of judgement on it, however, they might use an allegory (Animal Farm by George Orwell, about the rise of Communism in Russia) or some form of satire (Catch-22 by Joseph Heller, also about WWII).