A common mistake when writing adventures set in deserts is to assume that the climate is too ferociously hot to wear armor. Historically, most battles in deserts involved troops dressed in protective armor. Although they would have been miserable during the hottest part of the day or the hottest part of the year, desert weather isn't intolerably hot 24/7.
The Rhenn Plains are serene and peaceful, beautiful, and quiet as if nothing had ever had happened to it, hiding away it's violent present and past. During some time ago, the countries needed land to fight on, for they did not want war to come to their home, so they chose the Rhenn Plains, Armies met there and men died on the lands, so the land has been empty always. But now there has been set an outpost and they are beset by the goverments wanting to keep it free, will the soldiers of the barracks prevail, or fall trying?