Those troops are all on horseback, a super powerful retinue numbering in the thousands. Troops you build start out in your capital, so it behooves the enterprising khan to keep the center of governance near the action.
You can change capitals periodically, as you continue your migrations, and everything you’ve built comes with you. You can only manage empty land, and of that you can only build improvements in your capital province. The land that you gain isn’t managed like feudal societies. Combined with the stability hit you get if you’re at peace for too long, it essentially forces your hand to keep spreading ever westward. Or, in game fiction terms, you get too cramped in your corner of the steppes so you go get more land. This means invasions of neighboring countries, which have a nice carrot in the nomadic ability to gain an invasion casus belli if their population hits a certain percentage of its max. Where everyone else has to build and improve castles while juggling the loyalties of vassals on the feudal pyramid, nomads are mostly after empty land for their herds. The titular horse lords play very differently. Everyone built buildings in largely the same fashion and went to war in the same way. Those nomad mechanics offer a pretty big change from what CK2 has offered up until now. There’s a pretty wide variety of cultures to pick from if you want access to the new nomad mechanics, probably more than I was expecting. This primarily means the Mongols of Genghis Khan, but also includes groups like the Magyars and Cumans. Into the already complicated DLC basket of CK2-a basket which has added everything from Muslim caliphates to Zoroastrian satrapies to the base game’s Western European feudal shenanigans- Horse Lords revamps the play of steppe nomads to make them more unique and historically accurate.
The fact is that a full overview of everything about CK2 that has come before is outside the scope of this review Paradox’s most successful title is, at this point, a sprawling epic of betrayal, strange marriages, and backstabbing nobility which would make George R.
An assumption: if you’re reading this review of Horse Lords, Crusader Kings II‘s most recent expansion, you’re at least passingly familiar with the game and the quirky legends which have built up around it.