There is evidence to show that the kingdom over which Isperich and Crum ruled was not confined to the Lower Moesia, the country between the Danube and the Balkan range. There is no doubt that their sway extended over the lands which form the modern kingdom of Roumania; and it is possible that the sway of Crum extended over Siebenbürgen or Transylvania.
The extension of Bulgaria north of the Danube in the time of Crum is proved by a passage in the Anonymous writer of the ninth century, of whose work a fragment on the reign of Leo V. is preserved (see above, vol. viii. Appendix, p. 403). There we find “Bulgaria beyond the Danube” (ἑκει̑θεν του̑ Ἱστρου ποταμου̑, in the Bonn ed. of Leo Grammaticus, p. 345); Crum transported a multitude of prisoners thither. This is borne out by the Bavarian geographer of the ninth century, who mentions the country of the Bulgarians as one of the countries north of the Danube. 1
The chief evidence cited for Bulgarian dominion over Transylvania in the ninth century is the enumeration of a number of Dacian towns as belonging to the regions occupied by the Bulgarians, in the Ravennate Geographer; 2 and the circumstance that the Bulgarians used to sell salt to the Moravians 3 (there being salt mines in Transylvania, and none in Bulgaria south of the Danube).
To an unbiassed inquirer the evidence certainly renders it probable that during the 8th century when the Avar monarchy was weak and soon about to yield to the arms of Charles the Great, the Bulgarians extended their power over the Slavs and Vlachs of Siebenbürgen. This was certainly what under the circumstances was likely to happen; and the scanty evidence seems to point to the conclusion that it did happen. There is no reason to suppose that a part of the Bulgarian people settled in Siebenbürgen; only that Siebenbürgen was subject to the princes of Bulgaria during the ninth century until the Magyar invasion. Unfortunately, this question is mixed up with the burning Roumanian question; and the Hungarians firmly reject the idea of a Bulgarian period in Siebenbürgen. The first active promulgator of the view seems to have been Engel, 4 and Hunfalvy devotes several pages to the task of demolishing the “képzelt tiszai Bolgárság,” as he calls it, “the imaginary Bulgaria on the Theiss.” 5 The Roumanians welcome the notion of a northern Bulgaria, because it would explain the existence of the Bulgarian rite in the Roumanian church, and deprive the Hungarians of an argument for their doctrine, that the Roumanians are late intruders in Transylvania and carried the Bulgarian rite with them from the country south of the Danube.
But, apart from the Transylvanian question, there can be no doubt that Bulgaria included Walachia and extended to the Dniester under the early kings. There is no reason to suppose that when Isperich passed south of the Danube he gave up his dominion in Bessarabia. That Bessarabia was Bulgarian in the 8th century seems a permissible inference from the statement in the legend of the five sons of Kuvrat (see last note). And the fact that there was no other rival power to hold these regions seems to me to be almost conclusive. I am ready even to hazard the hypothesis that the influence of the Bulgarian kings in the 8th century extended as far as the Dnieper. Until the Hungarians came and took possession of Atelkuzu (see Appendix 7, p. 398), there was no other great power nearer than the Khazars. On the Dnieper, during the first half of the 8th century, the Bulgarians would have been in contact with their own kinsfolk.