If you want to control everything there are multiple different formations, stances, and special abilities for each type of unit – as well as things like stamina and morale to consider whenever giving them an order. There are much more complicated details beyond that, but the natural flow of the game means that there’s plenty of time to learn about them as you go. But while you’d think that controlling literally thousands of soldiers all at once would be horribly confusing the basics are as simple as pointing and clicking where you want a group to move to, or who you want them to fight. But Attila offers only relatively minor change, with the siege system being tweaked once again and the way fire behaves and spreads being made more realistic. The battles are clearly the sexier side of the game, and the bits you always seen in all the trailers.
This is no doubt entirely realistic but it’s not terribly interesting, especially when you have to start comparing all the different buffs and bonuses each family member offers. Having to maintain your family tree, and watching out for rivals, works a lot more like Medieval II than Rome II’s high politics.