Krum's Advances — Territorial expansion of Bulgaria during the reign of Khan Krum (803-814)
During his reign the Bulgarian territory doubled in size, spreading from the middle Danube to the Dnieper and from Odrin to the Tatra Mountains.
Photo Credit: By Kandi - Own work, CC BY-SA 4.0, https://commons.wikimedia.org/w/index.php?curid=3211315