For a long time, the kobolds believed that they were the only ones underground. But several centuries ago, they were unlucky enough to run into the gnomes. The shorties outnumbered the kobolds and had advanced mechanisms. So they decided to conquer the peaceful miners. The gnomes destroyed several kobold colonies and took their underground cities for themselves. The peaceful creatures had no choice but to hide. They could not hide in the underground adits for long, because the gnomes could find them at any moment. So they decided to act. They created squads of kobold defenders who fought back the invaders. Many gnomes and kobolds died in that underground war. And even though there is an uneasy peace between these peoples now, the kobolds did not disband the kobold defender squads in case the shorties again decide to show that they are the true rulers of the underworld.