▁appointment ▁by ▁August us ▁in ▁ 2 ▁BC ▁of ▁two ▁Pra et or ian ▁pre fect s , ▁Quint us ▁Ost or ius ▁Sc ap ula ▁and ▁Pub lius ▁Sal vi us ▁A per , ▁although ▁organization ▁and ▁command ▁were ▁en hanced . ▁T ac it us ▁reports ▁that ▁the ▁number ▁of ▁coh ort s ▁was ▁increased ▁to ▁twelve ▁from ▁nine ▁in ▁AD ▁ 4 7 . ▁In ▁AD ▁ 6 9 ▁it ▁was ▁briefly ▁increased ▁to ▁six teen ▁coh ort s ▁by ▁Vit elli us , ▁but ▁V esp as ian ▁quickly ▁reduced ▁it ▁again ▁to ▁nine . ▁ ▁Under ▁the ▁Jul io - Cla ud ian ▁dynast y ▁ ▁In ▁Rome , ▁their ▁principal ▁duty ▁was ▁to ▁mount ▁the ▁Guard ▁at ▁the ▁house ▁of ▁August us ▁on ▁the ▁Pal at ine , ▁where ▁the ▁centuries ▁and ▁the ▁tur ma e ▁of ▁the ▁coh ort ▁in ▁service ▁mounted ▁the ▁guard ▁outside ▁the ▁em peror ' s ▁palace ▁( the ▁interior ▁guard ▁of ▁the ▁palace ▁was ▁mounted ▁by ▁the ▁Imperial ▁German ▁Body guard , ▁often ▁also ▁referred ▁to ▁as ▁Bat avi , ▁and ▁the ▁St ator es ▁August i , ▁a ▁sort ▁of ▁military ▁police ▁which ▁were ▁found ▁in ▁the ▁general ▁staff ▁headquarters ▁of ▁the ▁Roman ▁Army ). ▁Every ▁afternoon , ▁the ▁trib un us ▁coh ort is ▁would ▁receive ▁the ▁password ▁from ▁the ▁em peror ▁personally . ▁The ▁command ▁of ▁this ▁coh ort ▁was ▁assumed ▁directly ▁by ▁the ▁em peror ▁and ▁not ▁by ▁the ▁Pra et or ian ▁pre fect . ▁After