In the West, with the decline of imperial power from the 4th century onwards in the face of the barbarian invasions, sometimes Christian bishops of cities took the place of the Roman commander, made secular decisions for the city and led his own troops when necessary. Later relations between a prince-bishop and the burghers were not invariably cordial. As cities demanded charters from emperors or kings and declared themselves independent of the secular territorial magnates, friction intensified between burghers and bishops.