Final answer:
The word that best fits the definition is 'praetorians'. The Roman emperors began to rely on them for the army. They were initially bodyguards to the emperor and grew powerful enough to influence who became emperor.
Step-by-step explanation:
The word that best fits the definition is 'praetorians'. The Roman emperors began to rely on the Praetorian Guard essentially as their personal army. The praetorians were initially bodyguards to the emperor, but they grew in power and eventually contributed to the military and political affairs of the Roman Empire, even to the point of deciding who would become emperor. Their influence on the Roman emperors made them a very significant entity in Roman history.
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