In AD 167 the Roman legion V Macedonica, returning from the Parthian War, moved its headquarters from Troesmis in Moesia Inferior to Potaissa in Dacia Porolissensis, to defend the Dacian provinces against the Marcomannic attacks. Other auxiliary units from Moesia Inferior participated in the middle Danube campaigns, leaving the lower Danube frontier defenses weakened. Taking the opportunity, in 170 or 171, the Costoboci invaded Roman territory. Meeting little opposition, they swept through and raided the provinces of Moesia Inferior, Moesia Superior, Thracia, Macedonia and Achaea.