Amur river in the context of "Natural border"

Manchuria is a historical region in northeast Asia encompassing the entirety of present-day northeast China and parts of the modern-day Russian Far East south of the Uda River and the Tukuringra-Dzhagdy Ranges. The exact geographical extent varies depending on the definition: in the narrow sense, the area constituted by three Chinese provinces of Heilongjiang, Jilin, and Liaoning as well as the eastern Inner Mongolian prefectures of Hulunbuir, Hinggan, Tongliao, and Chifeng; in a broader sense, historical Manchuria includes those regions plus the Amur river basin, parts of which were ceded to the Russian Empire by the Manchu-led Qing dynasty during the Amur Annexation of 1858–1860. The parts of Manchuria ceded to Russia are collectively known as Outer Manchuria or Russian Manchuria, which include present-day Amur Oblast, Primorsky Krai, the Jewish Autonomous Oblast, the southern part of Khabarovsk Krai, and the eastern edge of Zabaykalsky Krai.

The name Manchuria is an exonym (derived from the endonym "Manchu") of Japanese origin. The history of "Manchuria" (Manzhou) as a toponym in China is disputed, with some scholars believing it was never used while others believe it was by the late 19th century. The area was historically referred to by various names in the Qing dynasty such as Guandong (East of the Pass) or the Three Provinces referring to Fengtian (Liaoning), Heilongjiang, and Jilin. Manchuria as a geographical term was first used in the 18th or 19th centuries by the Japanese before spreading to Europe. The term was promoted by the Empire of Japan in support for the existence of its puppet state, Manchukuo. Although the toponym is still used, some scholars treat the term with caution or avoid it altogether due to its association with Japanese colonialism. The term is deprecated in China due to its association with Japanese imperialism and ethnic connotations. As a result, areas once considered part of Manchuria are simply referred to as the Northeast. The Three Provinces and the Northeast were also in concurrent use among the Japanese along with Manchuria until the Mukden incident of 1931.

The Treaty of Nerchinsk of 1689 was the first treaty between the Tsardom of Russia and the Qing dynasty of China after the defeat of Russia by Qing China at the Siege of Albazin in 1686. The Russians gave up the area north of the Amur River as far as the Stanovoy Range and kept the area between the Argun River and Lake Baikal. This border along the Argun River and Stanovoy Range lasted until the Amur Annexation via the Treaty of Aigun in 1858 and the Convention of Peking in 1860. It opened markets for Russian goods in China, and gave Russians access to Chinese supplies and luxuries.

The agreement was signed in Nerchinsk on 27 August 1689. The signatories were Songgotu on behalf of the Kangxi Emperor and Fyodor Golovin on behalf of the Russian tsars Peter I and Ivan V.