During his reign the Bulgarian territory doubled in size, spreading from the middle Danube to the Dnieper and from Odrin to the Tatra Mountains.

This resulted in the establishment of a common border between the Frankish Empire and Bulgaria, which would have important repercussions for the policy of Krum's successors.

His savagery went to the point that he ordered to bring their small children, got them tied down on earth and made thresh grain stones to smash them."

While Nikephoros I and his army pillaged and plundered the Bulgarian capital, Krum mobilized as many soldiers as possible, giving weapons to women and even to peasants.

The Byzantine army was wiped out in the ensuing battle and Nikephoros was killed, while his son Staurakios was carried to safety by the imperial bodyguard after receiving a paralyzing wound to the neck.

In 812 Krum invaded Byzantine Thrace, taking Develt and scaring the population of nearby fortresses to flee towards Constantinople.

Unwilling to compromise from a position of weakness, the new Emperor Michael I refused to accept the proposal, ostensibly opposing the clause for exchange of deserters.

Encouraged by this success, Michael I summoned troops from the entire Byzantine Empire and headed north, hoping for a decisive victory.

In front of the walls of the Byzantine capital, the ruler performed impressive pagan sacrifices of people and animals.

Already at the beginning of the meeting, the Bulgarian ruler noticed the signs that the Romans were making to the soldiers waiting in ambush, and although he was wounded, he managed to escape.

[7] Enraged by the baseness of the Romans, Krum ordered the looting and burning of churches and monasteries in Eastern Thrace.

Although Krum realized the defensive capabilities of the Byzantine capital, he ordered massive preparations for the attack on Constantinople to begin, which included Slavs, Avars and special siege equipment ("turtles", battle towers, "rams", flamethrowers, etc.).