Treaty of Aigun
In 1858, during the Second Opium War, China grew increasingly weaker as the "Sick man of Asia" while Russia strengthened and eventually annexed the north bank of the Amur River and the coast down to the Korean border in the "Unequal Treaties" of Treaty of Aigun (1858) and the Convention of Peking (1860). Russia and Japan gained control of Sakhalin Island.