South Pacific Mandate

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South Pacific Mandate
Mandate of Empire of Japan



Location of the South Pacific Mandate in the western Pacific Ocean.
Capital Koror
Languages Japanese (official)
Austronesian languages
Political structure League of Nations Mandate
 -  1919–1926 Taishō (Yoshihito)
 -  1926–1947 Shōwa (Hirohito)
 -  1919–1923 (first) Toshirō Tezuka
 -  1943–1946 (last) Boshirō Hosogaya
Historical era Empire of Japan
 -  Treaty of Versailles June 28, 1919
 -  Pacific Islands Trusteeship July 18, 1947
Currency Yen, Oceanian Pound
Today part of  Palau
 Marshall Islands
 Northern Mariana Islands ( United States)

The South Pacific Mandate (南洋庁 Nan'yō-chō?, lit. South Seas Mandate) was the Japanese League of Nations mandate consisting of several groups of islands (modern-day Palau, Northern Mariana Islands, Federated States of Micronesia, and Marshall Islands) in the Pacific Ocean which came under the administration of Japan after the defeat of the German Empire in World War I.[1]


Early history[edit]

Under the terms of the Anglo-Japanese Alliance, after the start of World War I, Japan declared war on Germany on 23 August 1914.[2] The country participated in a joint operation with British forces in the Battle of Tsingtao to capture the German settlement in China's Shandong Province. The Imperial Japanese Navy was tasked with pursuing and destroying the German East Asiatic Squadron and protection of the shipping lanes for Allied commerce in the Pacific and Indian Oceans.[citation needed]

During the course of this operation, the Japanese Navy seized the German possessions in the Marianas, Carolines, Marshall Islands and Palau groups by October 1914.[2]

After the end of World War I, as determined in the Treaty of Versailles, Japanese occupation of former German colonies in Micronesia north of the equator was formally recognized, and Japan was given a League of Nations Class C mandate.[2]

The Nan'yō government built and maintained hospitals[3] and schools.[4]

Pacific War[edit]

During the 1930s, the Japanese Navy began construction of airfields, fortifications, ports, and other military projects in the islands controlled under the mandate, viewing the islands as "unsinkable aircraft carriers" with a critical role to play in the defense of the Japanese home islands against potential American invasion. These became important staging grounds for Japanese air and naval offensives in the Pacific War.[citation needed]

In addition to the islands' naval importance, the Japanese Army utilized the islands to support air and land detachments. The "island-hopping" strategy employed by the United States military caused the Japanese Empire to lose control of its Pacific possessions between 1943 and 1945.[citation needed]

The League of Nations mandate was formally revoked by the United Nations in July 1947, and the United States was made responsible for administration of the islands under the terms of a United Nations trusteeship agreement which established the Trust Territory of the Pacific Islands.[citation needed]


Militarily and economically, Saipan, in the Marianas archipelago, was the most important island in the South Pacific Mandate and became the center of subsequent Japanese settlement. Another important island was Truk in the Carolines archipelago, which was fortified into a major navy base by the Imperial Japanese Navy.[citation needed]

Headquarters of the South Pacific Mandate in Saipan.

The administration of South Pacific Mandate was managed by the Imperial Japanese Navy, which divided the region into six administrative districts reporting to naval headquarters in Truk. Later, in April 1922, civilian government was established in the form of a civil administration department which still reported to the local naval garrison commander in each of the six administrative districts: Saipan, Palau, Yap, Truk, Ponape and Jaluit Atoll.[citation needed]

Later, the headquarters of the South Pacific Mandate was transferred from Truk to Koror, Palau, and its governor reported directly to the Prime Minister of Japan. However, after the establishment of a Ministry of Colonial Affairs, the mandate's governor was ordered to report to the colonial minister in June 1929.[citation needed]

When colonial affairs were absorbed into the Ministry of Greater East Asia in November 1942, the primacy of the Imperial Japanese Navy was again recognized by appointing an admiral as governor. Furthermore, the six administrative districts were reduced to three in November 1943: North, East, and West.[citation needed]


The population of the South Pacific Mandate was too small to provide significant markets and the indigenous people had very limited financial resources for the purchase of imported goods. The major significance of the mandate to the Empire of Japan was its strategic location, dominating sea lanes across the Pacific Ocean and providing convenient provisioning locations for sailing vessels in need of water, fresh fruit, vegetables and meat. Later[when?], the islands became important coaling stations for steam-powered vessels.[citation needed]


The initial population figures (1919-1920) for the mandated territories included around 50,000 indigenous islanders. The total grew to 70,000 inhabitants in 1930, and more than 80,000 in 1933, as more Japanese settled in the islands.[5] In the census of December 1939, the total population was 129,104, of which 77,257 were Japanese (including ethnic Taiwanese and Koreans), 51,723 indigenous islanders and 124 foreigners.[citation needed]


The mandated territories produced significant quantities of sugar cane, bananas, pineapples, taro, coconuts, and other tropical farming products on a par with Taiwan. The islands also provided bases for the Japanese fishing fleet.[citation needed]

In terms of mineral products, many islands yielded phosphates for farming, especially from Angaur island, which produced some 60,000 tonnes per year. Bauxite was another segment of the colonial economic structure, although the mineral was only present in the Palau group. Large quantities of pearls, both natural and cultured, were extracted from the islands.[citation needed]

The islands also allowed for regular flight links for long range seaplanes such as the Kawanishi H6K2-L ("Mavis") of Dai Nippon Koku KK.[citation needed]

See also[edit]


  1. ^ Ponsonby-Fane, Richard. (1962). Sovereign and Subject, pp. 346-353.
  2. ^ a b c Ponsonby-Fane, p. 348.
  3. ^ Ponsonby-Fane, p. 350.
  4. ^ Ponsonby-Fane, pp. 350-351.
  5. ^ Peattie, Mark R. (1988). Nanʻyō: the rise and fall of the Japanese in Micronesia, 1885–1945, p. 155.


  • Beasley, W.G. (1991). Japanese Imperialism 1894-1945. London: Oxford University Press. ISBN 0-19-822168-1. 
  • Nish, Ian (1991). Japanese Foreign Policy in the Interwar Period. Praeger Publishers. ISBN 0-275-94791-2. 
  • Howe, Christopher (1999). The Origins of Japanese Trade Supremacy: Development and Technology in Asia from 1540 to the Pacific War. University Of Chicago Press. ISBN 0-226-35486-5. 
  • Peattie, Mark (1988). Nan'Yo: The Rise and Fall of the Japanese in Micronesia, 1885-1945 (Pacific Islands Monograph Series). University of Hawaii Press. ISBN 0-8248-1480-0. 
  • Peattie, Mark (1992). Nan'Yo: The Rise and Fall of the Japanese in Micronesia, 1885-1945 (Pacific Islands Monograph Series). University of Hawaii Press. ISBN 0-8248-1480-0. 

Further reading[edit]

  • Annual report to the League of Nations on the administration of the South Sea islands under Japanese Mandate. [Tokyo]: Japanese Government. (Years 1921 to 1938)
  • Arnold, Bruce Makoto. “Conflicted Childhoods in the South Seas: The Failure of Racial Assimilation in the Nan’yo”. The Tufts Historical Review Vol 4, No. 11 (Spring 2011) [1]
  • Herbert Rittlinger, "Der Masslose Ozean", Stuttgart, Germany, 1939
  • Cressey George B. "Asia's Lands and Peoples", X Chapter : "Natural Basis of Japan" (P.196-285), section "South Seas" (p. 276-277).,1946
  • Sion, Jules. "Asie des Moussons", Paris Librarie Armand Colin, (1928) I, 189-266, Chapter X "The Nature of Japan", section XIII "Japanese Colonial Empire" (p. 294-324), and section IV "Formosa and Southern Islands" (p. 314-320)
  • Book "Asia", Chapter X "Japanese Empire" (p. 633-716), section "The Japanese islands in South Seas".
  • Childress, David Hatcher,"The Lost City of Lemuria & The Pacific", 1988. Chapter 10 "The Pohnpei Island, in finding of sunken city"(p. 204-229)