Siege of Reillis
The Siege of Reillis was an early campaign of the Great Crusade. Waged when the Emperor and the young Horus fought side by side, the battle began when the Human fortified city of Reillis opposed assimilation into the Imperium. The anti-Imperial forces used secret tunnels to infiltrate the Imperial camp, sending swarms of shock troops across the Imperial Army lines. Unprepared and unarmored, the Emperor and Horus fought back to back until a Plasma blast sent the young Primarch reeling to the ground. The Emperor stood over the wounded Horus, refusing to give ground until reinforcements arrived and Imperial forces emerged victorious.