quote]It must be remembered that the actual punishment, that is the killing, was not performed by the offending legion.
Actually, they were usually clubbed to death by their own tent mates as I understand it. The reason for this was that those escaping the actual death, were still punished by being forced to kill one of the men who had shared all their labours up to that point. Crassus decimated during the slave revolt, and it was the offending legion who drew lots, and beat their own to death.
I believe during this and earlier periods, shame was a big motivator. And most legionaries after Marius would have preffered taking chances with the lots, to simply being disbanded, missing out on their accumulated pay, land allotment etc.