The only sphere in which Nikephoros had some success was his campaign against Bulgaria and its chief, Krum, invading the country on two occasions and both times emerging victorious, even sacking the capital, Pliska. His treatment of the defeated populace was brutal, however: he rounded up all the children of the conquered cities and beat them to death with millstones. The chronicles of later historians are not necessarily to be trusted, but there can be little doubt that Nikephoros was not magnanimous in victory.
After his defeat, Krum tried to make a peace treaty with Nikephoros, but the arrogant and victorious emperor refused to negotiate and pursued him into the mountains, where he intended to annihilate the Bulgars once and for all. This was a terrible mistake: the entire Byzantine army set up camp in an area that could not be easily defended, and the opportunistic Krum attacked the Byzantines as they slept. It was a massacre, and the Byzantine army was destroyed. Nikephoros was slain on the battlefield, the first emperor to die in battle for 400 years. In retaliation for Nikephoros's previous atrocities, Krum had the Byzantine emperor decapitated and his skull lined with silver, to be used as a goblet. For years to come, visiting Byzantine dignitaries were forced to drink from the skull of their former emperor.
- Entry for Byzantine Emperor Nikephoros I (r.802-811 AD), in Kevin Lygo, The Emperors of Byzantium, London, 2022, p.138.