Quote Originally Posted by Lokiss View Post
Weird, it's not on my tech tree... O_o...
No, there wouldn't be. The unit side of the tech tree doesn't give any indication that some units are era-dependent. Cynwulf is also correct in that there was a bug in the unpatched version of vanilla MTW allowed you to train any of your faction's units as long as you had the requisite buildings, regardless of era. Thus, the English could train Longbows in the Early period, and the Byzantines could recruit Varangian Guards in the Late period.

Spoiler Alert, click show to read: 
Heh. I suddenly remember being very confused as a newbie when, after installing the 1.1 patch, my Egyptians suddenly couldn't train Mamluk Cavalry anymore (it was only around 1150 at the time). I was finally forced to ask about it in the forums here when I couldn't figure out what the heck had happened.