How were Roman emperors chosen in the ancient Rome?

Those 4 blue and one green bars are the 'five good emperors' — the longest period of peaceful succession in Roman history. .... read more

Some were chosen by the Praetorian Guards, who were the only standing military force in Rome itself (Claudius, Otho and many many others in the last two and a half centuries of the empire), some were chosen by the Senate (Nerva) and many seized power at the head of legions, starting of course with Augustus. read more

For most of this period, emperors were not chosen on the basis of their ability or honesty, but simply because they were born in the right family. For every great leader, such as Augustus, there was a tyrant like Caligula. read more