A balkan army general named Trajan Decius led his soldiers to incredible victories during the 249 campaign against Germanic tribes. In order to put Trajan Decius in charge, his soldiers killed Philip I and his son and proclaimed him emperor. But the death on the battlefield of the newly crowned emperor Decius and his son occurred in 251. In response, Gallus was named emperor by the senators of Rome. The army did not like him, so they killed him in 253 and placed Aemilianus in charge. This kind of nonsense continued for almost five decades.
While emperors, usurpers, soldiers, senators and more fought each other in this perpetual civil war, nobody was really in charge. As a result, the borders became more vulnerable. For the protection of the border and management of the local population, local rulers rose to power and claimed greater autonomy. A famous example is the Gallic empire.
