Sap Points.... I'm just curious, what did they actually do....

[Cute Wolf]

I have read some refrence of sapping works, but only dated in Medieval period... that's why I'm curious if the soldiers of antiquity could do the feat without proper exsplosives.... I can think of the mechanism behind fire burning under the walls, and gas-exspansion that led to tunnel collapsion (and finally wall collapsion)... but who had the good Idea for the first time?

And do the sapping ability are remnants of Vanilla that RTW left, as Ludens allready points out?