The equites praetoriani are the praetorian cohorts attached cavalry arm. They are equipped and fight mostly in the same way as normal ala of the auxilia.
New Praetorians can only be trained in their garrisons in Latium, the Empire’s heart, where they protect Roma, the seat of the imperial government.
The Cohortes Praetoriae are the highest ranked units in the whole imperial army. The equites praetoriani are their attached cavalry arm. They are equipped and fight in the same way as normal units of the auxilia. Their riders wear scale or chain mail shirts, iron helmets and long hexagonal shields for protection, while everyone is armed with a either type Mainz gladius or Celtic style longsword, ancestors of the spatha, the first real roman cavalry sword, a hasta lance and several iacula, light javelins. Like most of the roman cavalry units they use the famous four horned saddle, which enables a firm seat in almost all occasions. In the field the equites praetoriani often proved to be an efficient force. Their lack of experience in actual combat is largely compensated by excellent continuous training and capable officers.
Historically, Augustus added cavalry to the praetorian guard to improve its overall usefulness as an all-round fighting force. Unlike their infantry counterparts, most emperors did not rely on the equites praetoriani alone and most times strong independent horse guards coexisted with them - units such as the corpus germanis custodes until 68 AD and the equites singulares augusti from the 90's onwards.
In the late republic generals begun to form cohorts of elite legionnaires for their own protection and as an elite tactical reserve. They were called praetorians for guarding the "Praetorium", the tent or house of a Roman Army’s commanding officer. After the civil war Augustus reformed his praetorians into a permanent guard with nine cohorts of 500 infantry and approximately 90 cavalry. In campaigns the cavalry of the cohorts was often concentrated and operated independently as a single unit. Each of the cohorts was organized independently and commanded by an equestrian tribune. Three were stationed in Roma, the others in surrounding towns in Latium and Umbria.
In the early Principate, Praetorians were mostly recruited in central Italy and had to serve 16 years under excellent conditions and better pay compared to the frontier legions. After their discharge they received a high cash bonus, the praemia militare or a small piece of land. Later during Augustus reign the praetorian guard was commanded by two and eventually one praefect of equestrian rank, who soon thereafter became one of the most powerful man in the empire. In 23 AD Tiberius, influenced by his praetorian prefect Seianus, concentrated all cohorts in a single fort in Roma on the Viminal hill.