As far as I am aware, the earliest mention of the use of a stirrup in the Roman world comes from the Strategikon of Maurice, a Byzantine military manual dating from the late 6th Century AD. It is surmised by a number of Byzantine historians that the various wars between the Byzantines and the powerful steppe cultures of Late Antiquity, such as the Huns and the Avars, were a major contributing cause to the transformation of the Romano-Byzantine military throughout the 5th, 6th, and 7th Centuries. These interactions led to a heavy focus on cavalry combat and the adoption of a number of steppe technologies that would define Byzantine warfare for the next 700 years, including: the stirrup, the sabre (paramerion), the Avar-type bow, the arrow-guide (solenarion), and Eastern lamellar armor (what would become the klivanion).