The regiment was reconstituted in the late 1st century AD as a milliary ala, under the command of a tribunus militum. Initially, it contained 720 horse, divided into 24 turmae, or squadrons, of 30 men each. Numbers rose to around 1,000 under Hadrian (r. 117-38) and the regiment was expanded to 2,000 horse in the early 3rd century by the emperor Septimius Severus (ruled AD 197-211). The base constructed at this time for the expanded unit has been excavated underneath the Basilica of San Giovanni in Laterano, Rome (see Castra Nova equitum singularium).