A brave new world

In 1962, Britain and France discovered an old portal in Scotland. Repairing it allowed people to go through and be teleported to a new world, Hexan, with unique wildlife and inhabitants, populated by Kieren, fluffy humanoid creatures. After fortifying their position in the new world and setting up their main base at the portal's exit, a coalition made up of French and British soldiers was sent to secure the area. After days of exploration, the governments decided to make a permanent claim to the land so they could send the natural resources back to Earth. The natives weren't fond of invaders, so they started mobilizing. The lands that the coalition took belonged to the Kingdom of Tazann, which began bringing their army. Their technology is decades behind that of the humans, but they still have trucks, tanks, and guns, as they depended heavily on magic, which the humans are incapable of using. They don't have planes, as they use wild beasts to fly. Using this, they were able to push the coalition back hard, but the coalition simply brought more men, turning this into a stalemate.