 He believes that Byzantine Emperor Theophilos (r. 829–842) was forced to make concessions to Bulgaria, which may have included the incorporation of Philippopolis and its close surroundings into the Bulgarian Empire.During his time as co-ruler and "kavhan" of Malamir, Isbul financed the construction of a water conduit (aqueduct) or fountain in Pliska, which he donated to Malamir.That construction was the occasion for a great feast, which the ruler organised, and for gifts to the nobility, all of it testifying to Isbul's affluence.