Historical fiction, 450 AD. Attila the Hun invades Western Europe, destroying everything in his path. He lost, kind of, but not before leaving a really big scar. He is maybe as bad a guy as anyone in history. No doubt the Romans had it coming, but they stood for something at least, for civilization. All the Huns did was burn and kill.
Again I am interested why these tribesmen came off the Asian Steppe (High Plains) at least three times to obliterate everything they found. Maybe their culture reached a critical mass where cities and civilization were required to maintain a cohesive group, and instead of building them they let off the pressure by attacking far and wide. Living on the plains as I do now, I can see how living there made them really damn tough. It is just a hard place. Especially for a nomadic people living off the land.
The same thing happened here in North America. The Plains tribes were far and away the most formidable on this continent, and took to the horse as the center of their existence. Apaches, Comanches, Sioux, Crow, Nez Perce, etc. Lived in movable tepees. The land made the same culture and adaptations on two sides of the world. That is a thought I could follow a long way...
I think the Hyksos that attacked and occupied ancient Egypt around 2000BC, the Huns that attacked Rome and Europe around the 400AD, and the Mongols in the 1200's were the exact same crew, mostly unchanged but separated by centuries or millenia. From physical descriptions there is no doubt they were of the same race, and the cultural basis and geographical origin of each is identical, even to the yurts they lived in and tactics they used. And the weapons. Specifically the composite recurved bow paired with overwhelming mounted attack.