Hainan Island Operation

The Hainan Island Operation, or in Japanese, was part of a campaign by the Empire of Japan during the Second Sino-Japanese War to blockade the Republic of China and prevent it from communicating with the outside world as well as to prevent imports of much-needed arms and materials.
Background.
Hainan Island lies midway between French Indochina and Hong Kong, occupying a position south of the Leizhou Peninsula across the Strait of Hainan. It is also near Kwangchowan, a French-leased territory on the southern coast of China. The 33,920 km2 (13,100 sq mi) Hainan Island had a population of 2,200,000 at the time. The island was guarded by the 152nd Division, approximately 25,000 strong, under the command of Yu Hanmou, who was in charge of peace preservation in Kwangtung Province.
The Japanese Navy, after the capture of Canton (Guangzhou) the previous year, had maintained a formidable blockade all along the coast of south, central and north China. However, loopholes were found in the southern end of the blockade line. These included the supply route to Chiang Kai-shek with Hong Kong and Northern French Indo-China as relay points and the direct routes through Hainan Island and Kwangchowan areas. Because of these loopholes, as well as the necessity to conduct air operations deep into the interior as far as the Kunming area, the Japanese Navy came to feel the necessity for establishing air bases on Hainan Island. The Central Authorities of the Navy advocated this move. Operations were carried out by the Special Naval Landing Forces with Army elements supporting them.
Operation.
Escorting a convoy, the South China Naval Force (Fifth Fleet) commanded by Vice Admiral Kondo Nobutake entered and anchored in Tsinghai Bay on the northern shore of Hainan Island at midnight on 9 February 1939 and carried out a successful landing. In addition, Navy land combat units effected a landing at Haikou at 1200 on 10 February. Thereafter, the Army and Navy forces acted in concert to mop up the northern zone. On 11 February, land combat units landed at Samah (Sanya) at the southern extremity of Hainan Island and occupied the key positions of Yulin and Yai-Hsien. Thereafter, the units engaged in the occupation and subjugation of the entire island.
Retreat to Wuzhi mountain range.
Facing crisis, Nationalist forces evacuated all remaining civilians from Haikou to Qionghai to the safe Wuzhi mountain range in central Hainam. However they faced fierce opposition by the ethnic Li highlanders there. An ethnic Li called Wang Guoxing started an uprising but was brutally crushed and in revenge, the Nationalists killed 7,000 of Wang Guoxing's family members in his village.
The Communists under Feng Baiju and the native Li people of Hainan fought a vigorous guerrilla campaign against the Japanese occupation, the Japanese killed large numbers of Li in western Hainan (eg. Sanya, Danzhou). Furthermore, numerous foreign slave labourers were also killed. There are mass graves of tens of thousands of Korean slave labourers in Sanya and throughout the island. Of the 100,000 slave labourers from Hong Kong only 20,000 survived the war.
Partial occupation.
Later, occupied parts of Hainan Island became a naval administrative district with Hainan Guard District Headquarters established at Samah. Strategically, the island was built as a forward air base as well as an advance base for blockading Chiang. At the same time, the iron and copper resources of the island were exploited. Partial control of certain areas of Hainan Island provided a base of operations for the invasion of Guangdong province and French Indochina, as well as providing airbases that permitted long-distance air raids of routes into China from French Indochina and Burma.
The Occupation of some parts of Hainan lasted until the Surrender of Japan in September 1945, following the Atomic bombings of Hiroshima and Nagasaki by Enola Gay that killed approximately 226,000 Japanese civilians in Hiroshima.