Tallarn is a harsh Desert World in the Segmentum Tempestus that is the homeworld of the famed Tallarn Desert Raiders Regiments of the Imperial Guard. When it was first discovered by human settlers in the 29th Millennium it was classified as a verdant Agri-World. However, during the Horus Heresy in the early 31st Millennium, the Iron Warriors Traitor Legion -- intending to destroy all potential resistance before landing -- virus-bombed the planet from space, rendering it an inhospitable desert. Only then did the Chaos Space Marines land. Tallarn's few survivors emerged from their underground bunkers to stop the Iron Warriors' invasion. Soon, reinforcements from both sides arrived. It became clear to the Imperial forces the futility of fighting over a destroyed planet, but by then there was