Until the establishment of the Roman Republic and the office of consul, the king assumed the role of commander-in-chief. However, from about 508 BC Rome no longer had a king. The commanding position of the army was given to the consuls, "who were charged both singly and jointly to take care to preserve the Republic from danger".
Centurion, the principal professional officer in the armies of ancient Rome and its empire. ... The centurion thus nominally commanded about 100 men, and there were 60 centurions in a legion. Explanation:
the consuls
The commanding position of the army was given to the consuls, "who were charged both singly and jointly to take care to preserve the Republic from danger". The term legion is derived from the Latin word legio; which ultimately means draft or levy. At first there were only four Roman legions.