vytautas continued algirdas' vision to control as many ruthenian lands as possible. much of the territory was already under the grand duke's rule, but the rest was controlled by the mongols. tokhtamysh, khan of the golden horde, sought help from vytautas when he was removed from the throne in 1395 after his defeat by timur. an agreement was reached that vytautas would help tokhtamysh to regain power, and the horde would cede more lands to the grand duchy of lithuania in return. in 1398, vytautas' army attacked a part of the crimea and built a castle there. now lithuania spanned from the baltic sea to the black sea. a number of tatar captives were brought to ethnic lithuania.