OTL, the Sino-Russian border goes from the Mongolian-Russian-Chinese tripoint along the Argun river, stops at the confluence of the Ussuri river, then runs south along the Ussuri until it reaches the Tumen river. This border was determined by a series of Sino-Russian border agreements throughout the 19th century. TTL let's imagine a different agreed-upon border was constructed - either due to Russian satisfaction with Nikolayevsk-on-Amur being the main Pacific harbor or simple neglect on the Far East over more important matters in Europe, Russia gives up territories south of the Amur river entirely. Instead, they choose something like this - (Black: OTL, Red: TTL) By the 1860s of TTL, the red line becomes the boundary of the Sino-Russian border. If this was the case, how different would history in this region be? Will this affect the developments of Russo-Japanese relations? (It is assumed that the Great Game and Anglo-Russian hostilities continues as per OTL, but with less focus in this region) How significant will a Chinese harbor (and possible naval base) at the Sea of Japan be?