Union fell and was replaced by the Russian Federation in 1991. Sino–Russian relations since 1991 are currently close and cordial. Both countries maintain a strong geopolitical and regional alliance and significant levels of trade. Imperial period Lying at opposite ends of Eurasia, the two countries had little contact before about 1640. Both had to deal with the steppe nomads, Russia from the south and China from the northwest. Russia became a northern neighbor of China when in 1582–1643 Russian adventurers made themselves masters of the Siberian forests. There were three points of contact: 1) south to the Amur River basin (early), 2) east along the southern edge of Siberia toward Peking (the main axis) and 3) in Turkestan (late). The Oirats transmitted some garbled and incorrect descriptions of China to the Russians in 1614, the name "Taibykankan" was used to refer to the Wanli Emperor by the Oirats. South to the Amur (1640–1689) About 1640 Siberian cossacks spilled over the Stanovoy Mountains to the Amur River basin. This land was claimed by the Manchus who at this time were just beginning their conquest of China (Qing dynasty). By 1689 the Russians were driven back over the mountains and the Stanovoy Mountains remained the Russo-Chinese frontier from the Treaty of Nerchinsk (1689) to the Treaty of Aigun in 1859. For a full account see Sino–Russian border conflicts. Russian expansion eastward along the southern edge of Siberia Russian expansion in Siberia was confined to the forested area because the Cossacks were skilled in forest travel and were seeking furs while the forest natives were weak and the steppe nomads warlike. In the west, Siberia borders on the Kazakh Steppe. North of what is now Mongolia, there are mountains, Lake Baikal and more mountains until the Argun River separates Trans-Baikalia from Manchuria. West of Siberia, Russia slowly expanded down the Volga, around the southern Urals and out into the Kazakh steppe. Early contacts From the time of Kievan Rus' there was trade (fur, slaves) down the Volga to the Caspian Sea and Persia. Later trade extended southeast to the main Asian trade routes at Bukhara. Under the Mongol Yoke, Russian princes would regularly travel to Sarai for investiture. When Marco Polo returned from China he mentioned Russia as an obscure country in the far north. In 1466/73 Afanasy Nikitin made a journey southeast to India and left an interesting account. After the English