Treaty of Aigun
From the Treaty of Nerchinsk (1689) to the Treaty of Aigun (1858) its lower course was officially part of the border between Russia and China, although the border was not clearly marked and the area rarely visited. Some of Ivan Moskvitin's men reached the Uda in 1640. The local Lamuts told them of the rivers Zeya and the Amur but would not guide them inland. In 1684 some Cossacks fled from the Manchus on the Zeya, reached Udsk, and went up the Maya to Yakutsk.