Caesarean Legionnaires without armor?

[Tarbicus]

One thing springs to mind about being fired at during a siege is you are no doubt unusually close to the archers shooting arrows at you from the top of a wall, especially if you are at the base of a wall or gateway. Not only that, the arrows are no doubt firing down, not up into the air, and wouldn't lose any velocity. Maybe this has an effect on the stopping power of hamata, where it might be adequate during normal battle conditions? The closeness and downward velocity might give the arrow, at a complete and utter guess, twice the normal penetration, hence the need for something extra on top of your armour?