Treaty of Nerchinsk
By the 1640s Russian adventurers had taken control of the forested area north of Mongolia and Manchuria. From 1644, the rule of the Qing dynasty extended into China proper. In 1689 the Treaty of Nerchinsk established the northern border of Manchuria north of the present line. The Russians retained Trans-Baikalia between Lake Baikal and the Argun River north of Mongolia.