Northern Horsemen Tribes are a people of warfare whose military strength, understanding of warfare, and army size is great. Which is why the states of Qin, Zhao, and Yan have erected the great wall of borders facing their territory.
The Northern Horsemen tribes, are actually split into three major factions which constantly struggle for supremacy over one another. The Yueshi, Donghu, and Xiongnu. It is claimed that the Xiongnu were descended from the Kenjuu, an assertion that has some weight given that they share the same language.
150,000 Xiognnu warriors were killed right before the Battle of Bayou. In historical context, Mou Ten led a presumably successful campaign against them later into Sei's reign.