Complex sentence: The actual historical veracity of the Tiger Generals is unknown; the persons were known to exist, but whether or not they were actually granted these titles is uncertain: most likely this was a literary device used in the novel.
Split into simpler sentences: The actual historical veracity of the Tiger Generals is unknown; the persons were known to exist, but whether or not they were actually granted these titles is uncertain. Most likely this was a literary device used in the novel.