Ivan Asen I, also known as Asen I or John Asen I (; died in 1196), was emperor or tsar of Bulgaria from 1187/1188 to 1196 as co-ruler with his elder brother, Peter II. Hailing from the Byzantine theme of Paristrion, his exact place and date of birth are unknown. Although most contemporaneous chronicles describe Asen and his brothers, Theodor (Peter) and Kaloyan, as Vlachs, they were probably of mixed Vlach, Bulgarian, and Cuman ancestry. In 1185, Asen and Theodor went to see the Byzantine Emperor Isaac II Angelos in Thrace to demand an estate in the Balkan Mountains. After the Emperor refused and humiliated them, the brothers persuaded their Bulgarian and Vlach compatriots to rise up against the Byzantine Empire. Before the end of the year, Theodor was crowned Emperor of Bulgaria, taking the name Peter. After Isaac II defeated them in early 1186, Asen and Peter fled north over the Danube but returned in the autumn, accompanied by Cuman reinforcements. They captured Paristrion and began pillaging the nearby Byzantine territories. Asen became his brother's co-ruler in 1187 or 1188. They divided their realm around 1192, with Asen receiving Tarnovo and its region. Asen made a series of raids against Byzantine territories and expanded his rule over the lands along the Struma River in the early 1190s. A boyar, Ivanko, stabbed him to death in 1196. Early life The careers of Asen and his brother, Theodor, suggest they were descended from a prominent family, according to historian Alicia Simpson. Historian Alexandru Madgearu says their father was most probably a wealthy man who owned herds in the Balkan Mountains. Asen's birth date is unknown. The Synodikon of Tsar Boril calls him "Ioan Asen Belgun". One of the Lives of Ivan of Rila confirms that Ivan (or Ioan) was his baptismal name. His other two names are of Turkic origin: Asen came from a Turkic word meaning "sound, safe, healthy", Belgun from a word for "wise". The ethnic background of Asen and his brothers is still a source of controversy among historians. Chronicles written in the late 12th and early 13th centuries unanimously described them as Vlachs (predecessors of modern Romanians). Their close relationship with the Cumans, and the Turkic etymology of Asan's names, implies they were of Cuman or Pecheneg stock. According to a scholarly theory, the multiethnic character of their homeland, the Byzantine theme (or district) of Paristrion, makes