Thus , the country was divided on the eve of the Ottoman invasion , despite Ivan Shishman 's claims in his royal charters .
Contemporary chroniclers such as Johann Schiltberger speak of three regions , all of which were called Bulgaria .
The country was divided on the eve of the Ottoman invasion , despite Ivan Shishman 's claims in his royal charters .
Contemporary chroniclers such as Johann Schiltberger speak of three regions , all of which were called Bulgaria .