How important was individual skill in formation fighting?

[Nathan Ross]

I've read of some battles they were used as part of the battle array, but I've seen no reports specifically mentioning their success/failure.

During the civil war of AD69, Otho enlisted a unit of gladiators. Tacitus (Histories 2.11) calls them "a disreputable kind of auxiliary force — two thousand gladiators — but it was a means resorted to even by strict generals in civil war" (Sulla had also used gladiators in the previous century, to try and defend Rome, I think, against Marius).

Otho's gladiators were initially successful in a surprise assault against Vitellius's auxiliaries, but when called to defend a crossing of the Po river by a new force of Germanic auxiliaries, they did less well:

"Gladiators have not the same steadfast courage in battle as regular soldiers, and now in their unsteady boats they could not shoot so accurately as the Germans, who had firm footing on the shore; and when the gladiators in their fright began to move about in confusion so that rowers and fighters were commingled and got in another's way, the Germans actually jumped into the shallow water, held back the boats, and boarded them, or sank them with their hands." (Histories 2.35)

The end came for the surviving gladiators when the Vitellians brought up Batavian auxiliaries: "They had routed the gladiators who had crossed the river in boats, by meeting them with cohorts which cut them down while still in the water".

All this suggests that gladiators might have made quite good 'shock troops', but were less use in a straightforward battle - their training probably emphasised flashy moves and individual display more than endurance, discipline or 'steadfast courage'.

However, I do recall reading somewhere that a Roman commander used gladiators to train his troops at some point - I don't recall who or when; perhaps somebody else knows?