I am no expert but finally picked up BI and of course had to play the romans, hehe after watching Rome on HBO how could I not?..:) Anyways I noticed my starting troops didnt have any type of shield wall and after looking at the tech tree will any roman troops get it.

So I ask, how does a culture and unit in a previous game go from the only type of shield wall (turtle) to now being one of the few cultures who doesnt use it anymore? I always figured the Romans just got complacent but didnt realize they forgot their own inventions/tactics.