Before the outbreak of World War II in the Pacific, the island of Borneo was divided into five territories. Four of the territories were in the north and under British control – Sarawak, Brunei, Labuan, an island, and British North Borneo; while the remainder, and bulk, of the island, was under the jurisdiction of the Dutch East Indies.
On 16December 1941, Japanese forces landed at Miri, Sarawak having sailed from Cam Ranh Bay in French Indochina. On 1 January 1942, the Japanese navy landed unopposed in Labuan. The next day, 2 January 1942, the Japanese landed at Mempakul on North Borneo territory. After negotiations as to the surrender of Jesselton with the Officers-in-charge of Jesselton and waiting for troop reinforcements, Jesselton was occupied by the Japanese on 8 January. However, it took the Japanese until the end of the month to conquer the entire territory of British Borneo. The Japanese subsequently renamed the northern part as , Labuan as and the neighbouring Dutch territories as . For the first time in modern history all of Borneo was under a single rule.
British Borneo was occupied by the Japanese for over three years. They actively promoted the Japanisation of the local population by requiring them to learn the Japanese language and customs. The Japanese divided North Borneo into five provincial administrations (shus) and constructed airfields. Several prisoner of war camps were operated by the Japanese. Allied soldiers and most colonial officials were detained in them, together with members of underground movements who opposed the Japanese occupation. Meanwhile, local Malay leaders were maintained in position with Japanese surveillance and many foreign workers were brought to the territory.
Towards the end of 1945, Australian commandos were deployed to the island by US submarines with the Allied Z Special Unit conducting intelligence operations and training thousands of indigenous people to fight the Japanese in guerrilla warfare in the Borneo Campaign in preparation for the arrival of the main Allied liberation missions. Following landings in North Borneo and Labuan on 10June 1945 by a combination of Australian and American forces, the island of Borneo was liberated. The British Military Administration formally took over from the Japanese on 12September 1945.
Background
The Japanese intention to gain control of Borneo was associated with the concept of a unified Greater East Asia. This was developed by General Hachirō Arita, an army ideologist who served as Minister for Foreign Affairs from 1936 to 1940. Japanese leaders envisioned an Asia guided by Tokyo with no western interference and likened the Japanese Empire to an Asian equivalent of the Monroe Doctrine. The island was seen by Japan as strategically important, being located on the main sea routes between Java, Sumatra, Malaya and the Celebes. Control of these routes was vital to securing the territory.
With the Anglo-Japanese Alliance, Japanese immigrants had been welcomed since the 1900s. Companies such as Mitsubishi and Nissan were involved in trade with the territory. Japanese immigrants had also been in the Raj of Sarawak since 1915, with some of them working as hawkers and some Japanese women working in the red-light district. This presented opportunities for espionage, which were taken up by the Japanese military, especially from 1930. Secret telegrams revealed that the Japanese ships docking regularly at Jesselton were engaged in espionage. In 1940 the Americans and British had placed an embargo on exports of raw materials to Japan because of its continuing aggression in China and the Japanese invasion of French Indochina. Chronically short of natural resources, Japan needed an assured supply, particularly of oil, in order to achieve its long-term goal of becoming the major power in the Pacific region. Southeast Asia, which mostly consisted of European colonies, subsequently became a prime target for Japan. It hoped to obtain resources as well to ending the Western colonialism period.