The present paper deals with the problem of the Late Roman military titles development, the issue under consideration is thetitles of magister equitum (“amaster of cavalry”) and magister equitum et peditum (“a master of cavalry and infantry”). These titles were in the hands of generals, who held an office of master of soldiers (magister militum). The author concludes that Emperor Constantine I the Great, who established the offices of masters of soldiers, appointed two these generals, but each of these masters commanded both cavalry and infantry at the same time.