Jinzhou District
The Treaty of Portsmouth (signed 5 September 1905) ceded Port Arthur to Japan, which set up the Kwantung Leased Territory or "Guandongzhou" (), on roughly the southern half (Jinzhou District and south) of present-day Dalian. Japanese invested heavily in the region, which became the main trading port between Manchuria and Japan. Japan leased the area from Manchukuo after establishing that puppet state in 1932. In 1937, as the Second Sino-Japanese War began, Japan enlarged and modernized the trade zone as two cities: the northern Dairen (Dalian) and the southern Ryojun (Lüshun or Port Arthur).