Khan Krum was inherited from his son khan Omurtag (814-831). First of all the new ruler undertook the restoration of the Bulgarian capital Pliska which was burned down by the Roman emperor Nicephorus. After that he began a large building of new palaces, fortresses, roads and bridges.

In 816 khan Omurtag concluded a 30 year peace with the Byzantine Empire which confirmed the khan Krum's conquests in Thrace and Macedonia. Then the Bulgarian khan turned his aggressive politics to the west. He waged some wars with the Frankish kingdom and consolidated his power over Panonnia (present-day Hungary). The wars finished with a peace treaty concluded in 831 and Danube river became a border between Frankish kingdom and Bulgaria. The town of Pest (the eastern part of the present-day Budapest) was included in the borders of the Bulgarian state.

There is a large Bulgarian gold treasure from this period which has found 200 years ago in the Hungarian village of Nagy Saint Miklosh. Probably it has belonged to a Bulgarian noble who has lived in the western areas of the Bulgarian state.

Khan Omurtag accomplished very important changes in the administrative control of the state. At this time the particular Slav, Avar and other tribes had certain independence, i.e. the state was built on a federative basis. Khan Omurtag eliminated this independence and obliterated the boundaries between the tribes. He divided the country into eleven military-administrative areas and one of them was the capital Pliska. The khan appointed his trusted persons of the Bulgarian nobles to be governors of this areas. Many proto-Bulgarians, who before that lived in a narrow territory in Eastern Bulgaria, got dispersed in the new strategic centres all over the enormous country. In this way the process of population diffusion and building of the united Bulgarian nation speeded up.

The inheritors of khan Omurtag - khan Malamir (831-837) and khan Presian (837-852) renewed the expansion campaign against Byzantium. Khan Presian conquered the present-day southern Bulgarian mountains,  whole Macedonia and part of Albania. Thus at the middle of 9th century Bulgaria comprised the territories of Panonnia (present-day Hungary), Transylvania, Walachia (present-day Romania), Moldavia, Moesia, Thrace and Macedonia with their numerous inhabitants and already was European super-power. Bulgaria became the third European empire after the Roman and Frankish ones.