The Slavonic advance and the origin of the Bulgarian kingdom
After becoming politically established, the Bulgarians gradually widened their territorial possessions and collided with the compact Slavonic population of the neighboring provinces. The Bulgarian newcomers introduced military organization and discipline among the Slavs. Acting as a unifying element among the Slavonic tribes of the peninsula who had lived up to this time in separated groups, the Bulgarians gradually developed a powerful state which was, quite naturally, a great menace to the Byzantine Empire. In subsequent periods numerous military campaigns had to be organized by the Byzantine rulers against the Bulgarians and Slavs. Numerically weaker than the Slavs, the Bulgarian horde of Asparuch soon found itself under the great influence of the Slavonic atmosphere. Great racial changes took place among these Bulgarians; they gradually lost their original Hunnic (Turkish) nationality and became almost completely Slavonized by the middle of the ninth century, although even today they still bear their old name of Bulgarians.
In 1899 and 1900 the Russian Archeological Institute at Constantinople undertook to excavate the supposed site of the older Bulgarian seat (aul) and discovered extremely valuable survivals. On the site of the old capital of the Bulgarian kingdom (Pliska, or Pliskova) near the modern village of Aboba in northeastern Bulgaria, somewhat northeast of the city of Shumla (Shumen), the excavators discovered the foundations of the palace of the early Khans of Bulgaria and part of its walls with towers and gates, the foundations of a large church, inscriptions, many artistic and ornamental objects, gold and bronze coins, and lead seals. Unfortunately, these materials cannot be adequately evaluated and explained because the sources referring to this period are very scanty. One must confine himself at present to hypotheses and conjectures. Th. I. Uspensky, who directed the excavations, stated that the discoveries made by the Institute on the site of the camp near Shumla have brought to light very important data which afford sufficient basis for the formation of a clear idea about the Bulgarian horde which settled in the Balkans, and about the gradual transformations caused by the influence of relations with the Byzantine Empire. As evidenced by the earliest monuments of Bulgarian customs and manners, found during the excavation of their old capital, the same scholar said, the Bulgarians soon became subject to the cultural influence of Constantinople, and their Khans gradually assumed in their court the customs and ceremonies of the Byzantine court. The major part of the monuments unearthed during the excavations belong to an epoch later than the time of Asparuch, chiefly to the eighth and ninth centuries. The excavations are far from being completed.