The disintegration of Caslav's Serbia precipitated the rise of other Serbian principalities, most notably that of Duklja. This slavicized name comes from the ancient designation for a town (outside today's Podgorica) and part of the southern Adriatic and littoral - Dioclea. The region is to be called Zeta since the late 11th c., and eventually, since the late 15th c. - Montenegro ("Crna Gora" in Serbian).

Jovan (John) Vladimir appears during the protracted war between Byzantium and tsar Samuilo - the heir to the Bulgarian empire. In a situation reminiscent of earlier Serbian rulers, he is pressed by Bulgarian expansion, while being courted by the Byzantine emperor. Here Samuilo prevailed, taking Vladimir prisoner. His fate in captivity is the subject of one of the most romantic tales of early Serbian literature - the story of Vladimir and Kosara, an oral tradition reported in the 12th c. Chronicles of the Priest of Dioclea. The tale tells how Samuilo's daughter fell in love with the handsome captive and begged her father for his hand. He obliged, returning to his new son-in-law Duklja and adjoining Trebinje. Thereafter, Vladimir apparently ruled in peace, evading involvement in the major conflict that culminated with Samuilo's defeat by the Byzantines in 1014. During that time, Slavic Macedonian literacy and other ecclesiastic influences of the Ohrid patriarchate spread through his realm.

Vladimir finally fell victim in 1016 to a plot by his alleged ally, the last ruler of the First Bulgarian Empire, Jovan Vladislav. Duklja is not mentioned for the next 20 or so years, presumably remaining a vassal principality of Byzantium. Shortly after his death, Jovan Vladimir was to be recognized as a martyr and saint, with a cult that persists to this day, being honored on June 4. While limited in scope, this canonizing of the deceased ruler was to set a precedent, later to be expanded in the appearance of the holy Nemanjic dynasty in Raska.