Japan's View on the South Sea Islands before the Great War

The Japanese term Nan'yō guntō refers mainly to the Caroline, Mariana and Marshall Islands. These islands were under Japanese control from late 1914 until they were occupied by the U.S. navy in the course of the Pacific War (1941-1945). They are part of a larger, roughly defined area called Nan'yō (South Seas), which also includes South East Asia, and in some definitions the whole area between the Indian subcontinent in the West, and South America in the East. Strategic interests were the main drive for Japanese expansion into the Pacific, although questions of commerce and a perceived overpopulation in Japan were also important. Japanese involvement in the South Pacific dates back to the 1870s when commercial interests first began to be developed in the area. These efforts were encouraged by the navy, which was seeking to improve its standing relative to the army. At that time, most of the islands were under Spanish control. Later, all but Guam were German colonies and were administrated as part of the Schutzgebiet Deutsch-Neuguinea. In this context, the desire for a Japanese acquisition of the islands was first publicly voiced by journalists and authors aboard training tours with the navy, which was still in its infancy. Having experienced the area first-hand, they later wrote emphatically about the need for territorial expansion into the Pacific, believing there were still islands not yet claimed by western powers. At the same time, small Japanese firms were able to monopolise trade in the Marianas and the western half of the Caroline Islands from the end of the 1890s onwards, despite temporary setbacks due to German efforts to do the same.

The Japanese Occupation of the South Sea Islands

After Japan declared war on Germany on 23 August 1914 (due to their obligations under the Anglo-Japanese Alliance), two expedition corps called Nankenshitai, or the South Seas Squadrons, were established in order to destroy enemy fleets in the Pacific Ocean. These two squadrons occupied strategically significant islands of German Micronesia from October to December 1914. The warship Katori patrolled the Marianas and supported communications between the Japanese naval base in Yokosuka and the First South Sea squadron. At this juncture, they were asked by Great Britain to hand the islands over to Australia, who, along with the USA and New Zealand, opposed Japanese occupation of these island for strategic reasons, and because they desired to control the islands themselves. Despite Japan’s pledge to have no territorial ambitions upon its entry into the war, the Japanese government informed Great Britain on 21 November 1914 of its intention to keep the islands as spoils of war.

The occupation itself was peaceful because German warships had already left the islands before the Japanese navy arrived. German civilians, including governors, medical doctors, traders, mineworkers, and missionaries remained on the islands. German governors and their families were, however, deported immediately after the occupation. German missionaries were allowed to stay on the islands and continue their religious work under strict supervision until 1919. Neither the native inhabitants nor the Germans violently resisted the Japanese occupation. During the First World War, the navy took charge of administration, justice, education, religion, infrastructure, hygiene, sanitation, agriculture, and trade on the islands. Headquarters were established in Chuuk. After the Treaty of Versailles, Japan gained control of the German islands of Micronesia north of equator under its mandate authority. In March 1922, the naval government was replaced by a purely civilian administration called Nan’yō-chō, or the South Seas Government. A new government office was built in Palau at this time. Japanese rule of Micronesia continued until the American occupation during the Pacific War.

Japanese Media on the Occupation of Micronesia

In the years immediately prior to the outbreak of the First World War, a number of publications rekindled public interest in the South Pacific. Especially influential among these was Takekoshi Yosaburō's (1865-1950) 1910 best-seller Nangoku-ki. Japanese publications published during the war favoured keeping the islands under Japan’s control. As early as March 1915, some publications, for example the popular magazine Jitsugyō no Nihon, already discussed possible investments in the islands, demonstrating a belief that the islands would remain with Japan after the war. The same issue of Jitsugyō no Nihon featured an even greater number of articles about possible investments in South East Asia, whose markets could no longer be fully served by their colonial powers. Thus the focus of the mainstream nanshin, shifted from territorial expansion into the Pacific, to economic expansion into South East Asia. Other magazines, such as the Tōkyō keizai zasshi (“Tokyo economic magazine”), the very widely read Taiyō (“The Sun”) and Sekai bōken (“Adventurer's world”), discussed economic and political expansion southwards, favouring this over northward expansion. Popular arguments for expansion included the alleged kinship with the Micronesian populations and the civilising mission, which allegedly obliged the advanced Japanese people to help the primitive Micronesian people to develop.

Japanese Wartime Administration of the South Sea Islands

On 28 December 1914, occupying troops called Rinji Nan’yō guntō bōbitai, or the Provisional South Seas Defense Force, were established under a former commander of the Second South Seas Squadron, Rear Admiral Matsumura Tatsuo (1868-1932). Garrisons were dispatched from the headquarters in Chuuk with its five naval districts, Saipan, Palau, Pohnpei, Jaluit, and Yap (after 1915). By the end of 1915, primary schools were founded in each of the naval districts except Jaluit, which opened its first school in 1916. Further schools were later opened on the more remote islands. In the beginning, naval officers administered the schools with the assistance of sailors, Japanese merchants and educated indigenes. Afterwards, these professionals were replaced by civil teachers from Japan. Compulsory school attendance for all children was introduced and students were obliged to learn the Japanese language. In the beginning, German missionaries were permitted to continue their work unless they were suspected of conspiring against the Japanese. However, by the end of 1919, all German missionaries were banished under a condition of the Treaty of Versailles. In the early 1920s, German Catholics were replaced by Spanish Jesuits, and Protestant adherents were introduced by Japanese protestant missionaries from Nan’yō dendō dan (the South Seas Mission). American missionaries continued their work mainly on the Marshall Islands and in Kosrae. Moreover, the Japanese navy organised and executed a trip to Japan for inhabitants of Micronesia where the touring parties, called Nan’yō guntō tōmin kankō-dan, were able to visit urban areas like Tōkyō, Ōsaka, Kyōto and Kōbe. Almost all participants on this trip were influential locals such as clan chiefs. The aim of the trip was for the islanders to have an opportunity to develop a positive image of Japan as a country on par with Europe and the United States. Commerce and industry, especially related to copper and phosphate were encouraged. German firms, like the Südseephosphat-Aktiengesellschaft and the Jaluit-Gesellschaft, were expelled and were then succeeded by Japanese companies and the Japanese navy. Particularly, the strongest Japanese firm, Nan’yō bōeki kaisha (South Seas trading firm), enjoyed exclusive possession of trade and shipping rights in Micronesia.

Peace Talks in Versailles and Aftermath

Due to secret agreements made in 1917, Japanese claims to the South Sea Islands were supported by Great Britain, France, Russia and Italy. The USA opposed these claims, since this meant that Japan could quickly cut off U.S. access to the Philippines and, in case of a conflict, threaten Guam and Hawaii. Eventually a compromise was reached. Japan was awarded the formerly German islands north of the equator as a Class C League of Nations mandate. This allowed for the islands to be administered as an integral part of Japan, but forbade any fortifications. It mandated Japan to work for the (non-defined) advancement of the local populace, until it was sufficiently developed to be released into independence, although it was never specified when this point would be reached. Effectively this meant that Japan (and other mandate-holders elsewhere) could administer their assigned territories as quasi-colonies.

In World War II Japan used Micronesia as a naval base and an "unsinkable aircraft-carrier", from where the attack on Pearl Harbor was launched. During the Pacific War the U.S. invaded some strategically important islands and used them to bomb the main islands of Japan.


Niko Tillmann, Ruhr-Universität Bochum

Yuko Maezawa, Universität Bayreuth

Section Editor: Jan Schmidt