The way you control your tribe is through indirect orders. You can command various actions, but your tribe will ultimately do whatever they want.
For example, you can order your citizens to be hostile so that they'll attack the other tribes they come across ... but you can't tell them to attack a specific enemy.
Besides the different orders you can give, you can also alter the territory, creating forests, mountains, or bridges to connect different points on the map.
Visually Reprisal is a lovely game, and everything is very carefully designed. If you love pixel art, this game is great eye candy.
Reprisal is a fun strategy game. Behind its simple interface and relatively limited options is a wealth of complexity waiting to be discovered.