text: Early history of Shtokavian The early medieval Slavs who later spoke various Bulgarian and Serbo-Croatian dialects migrated across Moldavia and Pannonia. According to Frederik Kortlandt, the shared innovations originate from a "Trans-Carpathian" homeland, and by the 4th and 6th century, "the major dialect divisions of Slavic were already established". Dialectologists and Slavists maintain that when the separation of Western South Slavic speeches happened, they separated into five divergent groups, more specifically two, one Slovene and a second Serbo-Croatian with four divergent groups - Kajkavian, Chakavian, Western Shtokavian and Eastern Shtokavian. The latter group can be additionally divided into a first (Kajkavian, Chakavian, Western Shtokavian) and second (Eastern Shtokavian, Torlakian). As noted by Ranko Matasović, "the Shtokavian dialect, on the other hand, was from the earliest times very non-unique, with the Western Shtokavian dialects leaning towards Kajkavian, and the Eastern Shtokavian to Torlakian". According to isoglosses, and presumed end of existence of the common Southwestern Slavic language around the 8th-9th century, the formation of the Proto-Western Shtokavian and Proto-Eastern Shtokavian linguistic and territorial unit would be around the 9th-10th century (Proto-Western Shtokavian closer to Proto-Chakavian, while Proto-Eastern Shtokavian shared an old isogloss with Bulgarian). According to Ivo Banac in the area of today's Slavonia, Bosnia and Herzegovina (west of Brčko, Vlasenica and Neretva line) and on the littoral between the Bay of Kotor and Cetina, medieval Croats spoke an old West Shtokavian dialect, which, some believe, stemmed from Chakavian, while medieval Serbs spoke two dialects, old East Shtokavian and Torlakian. Many linguists noted a close connection between Chakavian and Western Shtokavian, for example Pavle Ivić saw Chakavian as an arhaic peripheral zone of Shtokavian, while Dalibor Brozović saw the majority of Chakavian dialects as derived from the same accentological core as Western Shtokavian. Western Shtokavian was principally characterized by a three-accent system, whereas Eastern Shtokavian was mostly marked by a two-accent system.