If you think a trihorn looks a lot like a triceratops with armor, that’s because it is. In a world where fuel has become costly and unreliable, the Kingdom of Balaska has turned to bioweapons for the future.
Kiel was the only city in the modern day Confederacy that wasn't destroyed when the bombs of the Last War fell. Therefore, the genetic repository built to stockpile the Earth's many species remained intact. This included species that never coexisted with humanity, but that were reverse engineered from more evolved organisms, such as birds.
Since their ressurection, trihorns have served as strong and reliable armored units capable of reaching considerable charging speeds. Thunderous and unstoppable en masse, they were pivotal in the final throws of the legendary Scratis Wars, and are still regularly used to overwhelm Horde camps and counter haliback and wikata charges.