 In the 10th century military treatise attributed to Emperor Nikephoros II, "On Skirmishing", it is stated that the cavalry army of any mobile army commanded by the emperor must be of at least 8,200 riders, not including 1,000 household cavalry—that is, the force belonging personally to the Emperor.These 8,200 horse ought to be divided "into 24 units of up to three hundred men each.These twenty-four units, in turn, just as with the infantry, should make up four groupings of equal strength, each with six combat units."