From as early as the 10th century, merchants and boyars of Novgorod had exploited the fur resources "beyond the portage", a watershed at the White Lake that represents the door to the entire northwestern part of Eurasia. They began by establishing trading posts along the Volga and Vychegda river networks and requiring the Komi people to give them furs as tribute. Novgorod, the chief fur-trade center prospered as the easternmost trading post of the Hanseatic League. Novgorodians expanded farther east and north, coming into contact with the Pechora people of the Pechora River valley and the Yugra people residing near the Urals. Both of these native tribes offered more resistance than the Komi, killing many Russian tribute-collectors throughout the tenth and eleventh centuries. As Muscovy gained more power in the 15th century and proceeded in the "gathering of the Russian lands", the Muscovite state began to rival the Novgorodians in the North. During the 15th century Moscow began subjugating many native tribes. One strategy involved exploiting antagonisms between tribes, notably the Komi and Yugra, by recruiting men of one tribe to fight in an army against the other tribe. Campaigns against native tribes in Siberia remained insignificant until they began on a much larger scale in 1483 and 1499.