Beasts…, Netflix’ first original movie production, is based on a novel by Uzodinma Iweala. The film contains graphic violence but I would not expect anything less due to the subject matter. The screenplay is fiction but hinged on real world civil wars occurring in Africa- where young boys are forced to join armies and are trained to kill for reasons that may very much be unclear. It stars young Abraham Attah and Idris Alba (Pacific Rim, Mandela, The Office). Director Cary Joji Fukunaga discusses details in making the film in this NYT article.
(“Beasts Of No Nation” is also a song recorded by Afrobeat king Fela Kuti in 1989- see following clip).