ENThis paper is the attempt to reconstruct the political background in the western possessions of Ulus Dzhuchyi, in which there was the Synovodska battle in 1362. Ic is shown that Lithuania captured concrete ulus - specific region, i. e. "Ulus Kurumyshy", better known as Podillya. Thus, this area was the part of the larger territorial-administrative unit of the Golden Horde - Wings Muvala. The advent and success of Algirdas was caused by the fact that Ulus Dzhuchyi to the 136l-1362's split into a number of independent principalities-possessions. And to the west of the Volga, after the defeat of Keldybek, there was no legitimate Khan (descendant Batu). At the same time the most powerful emir on these lands, Mamay, only began to gather around a prairie area and could not prevent the advancement of GDL. Moreover, the analysis of the economic situation in the region gives the reason to believe that there were the arrangements between emir and Algirdas. The main result of the battle was the way on the border to the Black Sea (between the rivers of the Southern Bug and the Dnieper) and, accordingly, "cutting" the western possessions of the Golden Horde, which laid the foundation for the creation o f the Budzhak Horde.