Quote Originally Posted by Simon Appleton
(b) how many extra casualties in a melee would you expect legionaires to suffer in battle as a result of not having shields - let's say 20% again
so roughly speaking, the shield-disabling effects of the pila might indirectly add 0.2*0.2*80=3.2 casualties to the direct kills.
Actually, on reflection, this is more complicated than I thought. The calculation implicitly assumed being shieldless would lead to 20% of the unit dying. In the text, I wrote it would lead to 20% more casualties. They are very different - e.g. if you only lose 5 men in a melee.

One "empirical" approach would be to set up a custom battle between two unit legionnaires, both with no pila and one without a shield. See how many more kills the shielded ones get before their enemy routs. Multiply that difference by the fraction of shield-disabling hits you think 80 pila would give and that is the extra casualties you can attribute to the pila from its shield disabling effect.

Of course, the results may differ between legionnaires and other units. Legions are relatively well armoured, so the shield may make less difference to their defence than it does to an unarmoured warband. But it'd be better than my hand-waving.

BTW: what's the archer bug in 1.5?