Confusion re: Useless Elite Cavalry Stables and trade caravan/silk road

[SuleymanGroznii]

I don't get how these upgrades work. I've been playing a Parthian campaign for quite a while; I'm in 232, I have all of Bactria, Epiphaneia is my western frontier, and my southern frontier is Phrada and the Alexandria first owned by the Seleucid Empire. I've upgraded just about all of them to Aux Phase 3 or Royal Barracks, public order is ridiculously high in most, and while plenty of them had Elite Cavalry Stables when I took them, I've never been able to train Kataphractoi or any other elite cavalry units with them!

That's not all. I just built an Elite Cavalry Stable in Hecatompylos, which I have upgraded like crazy, made my capitol (both my sad attempt at keeping it all historically accurate, and a move that massively increased my profits every turn), and I CAN'T TRAIN ANY ELITE CAVALRY!!! ARRHGHGHGHGHGHGHGHG!!!

What gives? I noticed that the description of ECSs in the building browser says that using them depends on a settlement's citizenship level, but how do you change that? Destroy all, or a lot of, the non-Zoroastrian stuff, Greek stuff, Buddhist stuff, etc?

Having to recruit all my Kataphractoi and Heavy Camels in Saramana to send them out all over their place was hell, so waiting six turns for an ECS that could more easily and more quickly send elite units to my eastern cities was like waiting six turns for Christmas; realizing that it was useless was kinda like getting mauled by a rabid llama--VERY demoralizing.

Also, what's up with the trade caravans, silk road, etc upgrades? I noticed that they don't do much for your income, but I'm thinking that maybe they do a lot more once all of your cities (or at least a circuit of them...) have one. That would make sense, at least.

Anyways, if anybody can answer these weird questions, it would be much appreciated. Thanks in advance, or at least thanks for trying

[Darkarbiter]

Silk roads are just like markets. I'm guessing elite cavlry don't do much in certain provinces probably because the Parthians never recruited cavlry from there.

[SuleymanGroznii]

Thanks, and egg on my face. I checked through the export data, and found that a city's elite cavalry stable apparently needs Royal Barracks. And I um...um...um...um...totally did not have Royal Barracks in that city, arghghghgh!!!

I got so mad that I just went back a few saves and started over, cause Herat's population is more than 14,000, and I wasn't aware that if you didn't build a Bazaar and a Councilor's chambers when the population gets to that point, people start going nuts...