The nearest territories are South Korea at north, Japan at east, and the People's Republic of China at west.
In 1936, the colony became a Insular Province and the Jejuans were granted the right to vote and Brazilian citizenship. Since then, Jeju and its citizens enjoy equal status to the provinces of Brazil with self-government and political representation. Also around this period investment in economic and social development of the province, especially tourism, industry, fishing and agriculture began to flow from Mainland Brazil.
The Jejuan standards of living are extremely high and its economy is wealthy and developed. If Jeju was a sovereign country, it would have the 3rd highest nominal GDP per capita and the 20th nominal total GDP in Asia, and it would have the highest standard of living in the continent by HDI (0,920).
Its motto is "Entre gigantes, somos maiores" (Portuguese: Among giants, we are bigger). This means that, even a small island among giants, like China and Japan, Jeju is not just Jeju, but also Brazil, a bigger nation.
According to legend, three demi-gods emerged from Samsung which is said to have been on the northern slopes of Mt. Halla and became the progenitors of the Jeju people who founded the Kingdom of Tamna.
It has also been claimed that three brothers—including Ko-hu—who were the 15th descendants of Koulla, one of the Progenitors of the Jeju people, were received by the court of Silla, at which time the name Tamna was officially recognized, while the official government posts of Commander, Prince and Governor were conferred by the court upon the three. However, there is no concrete evidence of when the "Three Names" (Samseong-Ko, Yang and Pu) appeared nor for the exact date of when Ko-hu and his brothers were received by Silla. It may be supposed that the "Three Names" Founding Period occurred during the Three Kingdoms (Goguryeo, Baekje and Silla) Period on the mainland of Korea.
Taejo, founder of Goryeo, attempted to establish the same relationship between Goryeo and Tamna as Tamna had had with Silla. Tamna refused to accept this position and the Goryeo court dispatched troops to force Tamna to submit. Ko ja-gyeon, chief of Tamna, submitted to Goryeo in 938 and sent his son, Prince Mallo, to Goryeo's court as a de facto hostage. In 1105 (King Sukjong's tenth year), the Goryeo court abolished the name Takna which had been used up to this time and, from that year on, the island was known as "Tamna-gun" (district) and Goryeo officials were sent to handle the affairs of the island.
Tamna-country was changed to Tamna-county in 1153 during the reign of King Uijong and Choi Cheok-kyeong was posted as Tamna-Myeong or Chief of Tamna. During the reign of Gojong of Goryeo, Tamna was renamed "Jeju" which means "province across the sea".
In 1271, General Kim Tong-jeong escaped with what remained of his Sambyeolcho force from Jindo and built the Hangpadu Fortress at Kwiil-chon from where they continued their fight against the combined Korean government-Mongolian army but within two years, faced by an enemy army of over 10,000 troops, the Sambyeolcho was annihilated.
During the Joseon Dynasty (1392-1910), Jeju islanders were treated as foreigners and Jeju was considered as a place for horse breeding and exile for political prisoners. In the 17th Century, Injo of Joseon issued an edict prohibiting islanders from traveling to the Korean mainland. Consequently, Jeju islanders staged several major uprisings, of which the last and major one was the Kang Rebellion (1845).
After the end of the Overseas Trading Company (COU) in 1835, Brazil inherited its colonial empire. Since then, the Brazilian colony of Weihai, in the Chinese Yellow Sea, grew much more as a trade hub, increasing Brazilian interest in the East Asia.
After the First Opium War (1839-1842), between Britain and the Qing China, the once powerful Chinese Empire signed its first unequal treaty, giving to the British the island of Hong Kong and many commercial privileges. That led the other great powers to impose on China their interests, weakening even more the Chinese power. Brazil, in 1844, was the first power after Britain to impose an unequal treaty on China. By the Treaty of Zhifu, China ceded to Brazil "to perpetuity" the sovereignty over Weihai, until then just a leased territory, extraterritorial and commercial privileges to Brazilian citizens, the status of Most Favored Nation in China and the right to trade in any of the Chinese ports opened to foreign trade by previous or future treaties.
Finally, Brazilian expansion interests in East Asia woul lead to the War of Jeju (1862-1864), a conflict between Brazil and the Joseon Kingdom (Korea). With a good trade base in Weihai, Brazil started to show interest in Jeju, sending secretly Christian missionaries and spies to destabilize the Joseon hold on the island. Jeju's location between the three major East Asian nations and its people's hate towards the Joseon made the island a "jewel that glowed to the eyes of Brazil"
During the Kang Je Geom Rebellion (1862), twelve Brazilian missionaries were arrested and sentenced to by the Joseon government for "instigaing revolution" in Jeju. Before the fulfilment of the sentence, he Governor of Weihai, Morgan Figueiredo, presented to the Joseon an ultimatum, sent to him by telegraph from the King Pedro II himself, to release the prisioners and send them unharmed to Weihai, where they would be returned to Brazil. The ultimatum was ignored by the Joseon who, to prove their authority, executed six of the twelve missionaries. Since the 1840s the missionaries lived and prozelityzed secretly in Jeju and a large portion of the Jejuan population was already Christian, a religion that was growing in influence in the Korean Peninsula. The public execution of half of the missionaries was seen by Brazil as an act of war and the Brazilian government ordered the governor Figueiredo to send a punitive armada, led by Commander Josan da Costa, to invade Jeju and bombard Korean coast settlements.
In Jeju, the Brazilians were received as liberators and, with the support of the Jejuans, expelled the Joseon authorities from the island. For the next months, the Brazilian fleet bombarded Korean coast and riverside cities. Fearfull of a possible Brazilian invasion, Regent Heungseon Daewongun step aside temporally from his isolationist policy and signed the Treaty of Jeju with the Brazilians, giving them the island with the promisse that Brazil would not try to interfere in Korea again. Although Brazil kept its word and did not interfere after the treaty's signing, the Joseon isolationist policy would face new obstacles from, mainly, France and the USA until its final disruption by the Japanese in 1876.
In 1865, Josan's Castle, a military fortress built to protect the Brazilian naval base in the island, was built. Called Josanseong or Josanseon by the Jejuans, the city of Josanseon (current Josanso) started to grow around the base in the early 1870s, soon becoming the island's largest city and port and, in 1902, its capital.
From 1860 to 1900, many Brazilians immigrated in Jeju, adding their culture to its cultural pool. The Brazilian government imposed on the Jejuans their education system (in Portuguese), and incentivated missionaries to exercise their activities in the island. That process of acculturation, by mixing Jejuan and Brazilian culture and imposing Portuguese, transformed completely the island. By the dawn of the 20th century, Jeju was known as the "Most Western Point of East Asia". Its economy was based completely in the naval base, fishing, agriculture and some small industries.
With the arrival of Japan as a imperialist power in the end of the 19th century, Jeju became a fortress for the Brazilian sphere of influence in East Asia. The Japanese influence grew more and more, until the annexation of Taiwan and, later, Korea, making a good relationship with Japan as one of the Brazilian main policies in the region.
After the World War I, Brazilian investments in Jeju grew and so did its industry. Jeju's economy grew continuously until the Crisis of 1929.
As a Insular Province
Just before the World War II, Japanese imperialism over East Asia and its militarism grew to a unsustainable level. Concerned with Jeju's and Weihai security, Brazil elevated Jeju to the status of Insular Province in 1936, turning it a constituent part of the Brazilian nation itself and no more a colony.
The elevation of Jeju prevented Japan of trying to use it as a base to its invasion of China one year later, as invading a constituent part of Brazil would lead directly to war without perspective of negociation. Jeju and Weihai remained untouched, as Japan did not want to have war with Brazil at time, at least not until Japan had a big power base in East Asia.
The Brazilian concerns were well directed. In 1941, just after the German invasion of Zenith and the destruction of the Brazilian Northern European Fleet, the Japanese invaded Jeju and Weihai and destroyed completely the Brazilian fleets there. Just after, Brazil declared war to the Axis Powers. The destruction of the Brazilian fleet in Jeju and the flotilla in Weihai, added to the latter invasion of Singapore, basically disrupted any Brazilian naval power in East Asia. The occupied Singapore, as well as the Dutch East Indies and Malaysia, were used by the Japanese as a wall, preventing any Brazilian fleet from the Indian Ocean to aid Jeju.
During the Japanese occupation, Jeju was used as a naval base for the Japanese campaigns at China. The Jejuan Resistance remained its activities until 1944. During that period, known in Brazilian history as the "Niponic Terror", many Jejuans were executed by the Japanese for supposed rebellious activities.
In 1944, after Brazilian offensives in Burma and the Dutch East Indies and the reconquering of Singapore, a Brazilian fleet achieved to recover Jeju, during the American-Japanese battles in the East. In the end of the war, the Brazilians (including many Jejuan soldiers) helped the Americans to invade Japan.
After World War II, the investments on Jeju increased greatly. As now a part of Brazil itself, Jeju gained importance in Brazilian internal policy and attracted new economic activities to the island.
Between 1945 and 1980, Jeju grew to become one of the wealthiest and highest developed regions of Asia. With great industrial and financial vocation, its standard of living is the highest in Asia (when it is counted among sovereign countries) and its nominal GDP per capita is 3rd highest.
Jeju is a Brazilian Insular Province. Despite the adjective (insular) it is, in practice, similar to any other Brazilian provinces in rights and duties. It means that it is an autonomous sub-national entity, having government (self-government, self-legislation and self-tax collecting) and its own constitution (Constitution of the Insular Province of Jeju), and that it is federated to other federal units of the country to form the Kingdom of the United Provinces of Brazil. As all of the Brazilian subnational entities, its government works as a presidential republic. The Executive Power is exercised by a Governor elected by universal suffrage for four years and the Judiciary by provincial courts of first and second instance that take care of common justice. Its legislature is an unicameral Legislative Assembly with elected deputies (representatives). The Legislative Assembly oversees the activities of the executive branch in the province and municipalities. The current governor is Fernando Quintana.
Since the aftermath of the Korean War (1950-1953) and the division of Korean into two distinct and rival nations, North Korea and South Korea, Jeju status as a Brazilian territory has been questioned by both. North Korea and South Korea both claim each other's territory present themselves as the true representative of whole Korea. South Korea relinquished its claims over Jeju in 2012, when Brazil, Japan and South Korea signed the Compromise of Busan against North Korea and its threats to the three countries. North Korea still claims Jeju as its rightfull territory.
The total population in the general census of 2015 was of 2,176,000 inhabitants, making Jeju by far the most populous of the Brazilian overseas provinces. By ethnicity, Jeju's population are 37% Asian, 22% Mixed, 18% White, 12% Black, 2% Polynesian and 1% Amerindian. 87,8% of Jeju's population live in Josanso, the capital, and its metropolitan area. Josanso has Brazil's 16th largest metropolitan area, with 1,910,000 inhabitants.
Christianity is the main religion of the province: the majority (38%) belong to various Protestant churches and a large minority (29%) are Roman Catholics. The largest congregation is the Lutheran Church. In addition, 21% of the population is Agnostic or Irreligious.
Portuguese is the only official language as is the first language of almost all the population. Jejuan, a dialect of Korean, is spoken by 1,000 to 3,000 people, though not as thr first language. Jeju has sizeable Filipino (8,000), Japanese (6,300) and Korean (5,100) immigrant populations.