In early 811, Nikephoros I undertook a massive expedition against Bulgaria, advancing to Marcellae (near Karnobat). Here Krum attempted to negotiate on July 11, 811, but Nikephoros was determined to continue with his plunder. His army somehow avoided Bulgarian ambushes in the Balkan Mountains and made its way into Moesia. They managed to take over Pliska on July 20, as only a small, hastily assembled army was in their way. Here Nikephoros helped himself to the treasures of the Bulgarians while setting the city afire and turning his army on the population. A new diplomatic initiative from Krum was rebuffed.