By the third century AD, the boundaries of Rome had grown far beyond the area enclosed by the old Servian Wall, built during the Republican period in the late 4th century BC. Rome had remained unfortified during the subsequent centuries of expansion and consolidation due to lack of hostile threats against the city. The citizens of Rome took great pride in knowing that Rome required no fortifications because of the stability brought by the Pax Romana and the protection of the Roman Army. However, the need for updated defences became acute during the crisis of the Third Century, when barbarian tribes flooded through the Germanic frontier and the Roman Army struggled to stop them. In 270, the barbarian Juthungi and Vandals invaded northern Italy, inflicting a severe defeat on the Romans at Placentia (modern Piacenza) before eventually being driven back. Further trouble broke out in Rome itself in the summer of 271, when the mint workers rose in rebellion. Several thousand people died in the fierce fighting that resulted.