Centurion Position in Battle

[Nathan Ross]

Tribunes were supposed to have 10 years of military experience first, though in the late republic that rule started to be watered down.

And in the empire more so. The tribune of the republic and the principiate was quite a different sort of officer. I think in Caesar's day they still tended to be young equestrians, eager to impress their chief with displays of virtus, in return for political and social advancement no doubt. By the early principiate the emperor was the sole patron of the equestrian officer, and with the institution of the tres militiae the equestrian no longer had to impress anybody on the battlefield to get ahead. We do still find inscriptions to legion tribunes who fell in battle, and some were no doubt vir militares, but far less so than in the republic.

By the later empire things change, and the tribune seems to re-emerge as a small unit commander, often risen from the ranks. Taking over from the centurion, in fact.

But I think you're right about the performance aspect of battlefield command - the centurion (and on occasion the tribune, even the legate) had not only to lead, but be seen to be leading!