The Kievan Rus’ were once a formidable power, but that strength shifted away from Kiev in the twelfth and thirteenth centuries. The reasons for this shift were numerous, and the power structures which came in Kiev’s place were also varied.
Indeed, according to A History of Russia to 1855, “there is considerable controversy about the precise nature of these factors [related to the decline and fall of Kiev] and no consensus concerning their relative weight” (Riasanovsky and Steinberg 36).… Read the rest here