What potential problem was created by the roman style of military leadership?

Answer 1

The professionalization of the army made the soldiers loyal to the commanders of their legions. During the Late Roman Republic these men could use their soldiers to obtain what they wanted through the threat of or the use of military violence. In 71 BC Crassus and Pompey encamped their troops outside Rome to have themselves elected as consuls (the two annually elected heads of the Republic). Pompey was not even eligible on the grounds of being below the required age and of not having served some public offices which were required before the consulship. In 88 BC Sulla entered the city of Rome with his troops during his first civil war against forces of Marius, even though Roman religion forbade the bearing of arms within the city walls. In the last 64 years of the Roman Republic there were 12 civil wars. The civil wars eventually brought the Republic down.

The problem persisted when the Republic was replaced by 503 years of rule by emperors. In 69 and 192-97 there were civil wars between men who fought over the title of emperor. The Crisis of Third Century (AD) was a period of military anarchy. Most of the emperors during this period were military commanders who were proclaimed emperors by their own troops. They were often murdered by soldiers, sometimes even their own troops. There were also 35 usurper emperors who tried to take over parts of the empire after having been proclaimed emperors by their troops. There were civil wars between contenders over power after this period as well. Again, they were made possible by their troops' loyalty to them. Even after the mentioned crisis there were quite a lot of usurper emperors backed by their own troops.