Aztec units retain, as far as I can see, their vanilla stats. This is ridiculous--Aztec forces were pathetic compared to European forces. Perhaps there can be one elite unit equipped with the macahuitl (an obsidian-edged club capable of inflicting horrific injuries), but other than that, we're talking about a walking joke of a civilization that didn't even have the wheel or bronze. The attack and defense stats should be greatly reduced. Attacking the Aztecs should be like punching a kid in the face.