How do trample mechanics work?

[Micah]

Think size difference matters in how many AP it takes to trample a square, not the damage...elephants seem to push a lot further than chariots when they trample from what I've seen. The other piece here is that I'd bet the trampling is applying the -2 defense for multiple attacks, which is why massed tramplers kill stuff so much faster than a lone unit...the unit's defense gets hammered down a lot more quickly when there are a lot of tramplers. This also explains why high defense units will lose to trample when it seems like they should be nearly immune to it.