Historically, krais were massive first-level administrative divisions in the Russian Empire, divided into large "guberniyas" (governorates). Following the numerous administration reforms during the Soviet era, the guberniyas were abolished and krais were reshaped into smaller, more numerous divisions. Eventually, krais and oblasts became almost totally equal as the top-level administrative division of the Soviet Socialist Republics (SSRs), the constituent political entities of the Soviet Union, with the only difference being autonomous oblasts could be subordinated to krais but not to oblasts. The krais were unique to the Russian SFSR and held very little autonomy or power, but when the Soviet Union dissolved into sovereign states along the lines of the SSRs, they became first-level administrative divisions of the Russian Federation and received much greater devolved power.