Sejong the Great

Yi Do was born in May 1397 in Hanseong, present-day Seoul, the third son of Prince Yi Bang-won and Queen Wongyeong. His grandfather Yi Seong-gye had founded the Joseon dynasty in 1392. In the following years Yi Bang-won seized power by force in a struggle among the princes and became King Taejong in 1400. In South Korea Sejong's birthday, 15 May, is now Teachers' Day.

Taejong strengthened central authority and curbed the power of aristocratic families and private armies. The young Prince Chungnyeong, as Sejong was then known, was regarded as diligent and well read. In June 1418 Taejong replaced his eldest son, Prince Yangnyeong, as crown prince with Chungnyeong and abdicated two months later.

From 1420 Sejong developed the Jiphyeonjeon, an academy of young scholars, into an institute for policy advice, historical research and the compilation of books. Works on agriculture, medicine, ethics and history appeared during his reign. He also had the tax system revised on the basis of soil quality and harvest yields.

The court had astronomical instruments, sundials and an automatic water clock (1434) built, with the engineer Jang Yeong-sil playing an important role. In 1441 a rain gauge was introduced, together with a system for recording rainfall throughout the country. A calendrical work adapted to the position of Seoul was also produced.

In 1443 Sejong, with the help of scholars from the Jiphyeonjeon, completed a phonetic alphabet for the Korean language, promulgated in 1446 as 'Hunminjeongeum', 'the correct sounds for instructing the people'. It originally had 28 letters, partly based on the shape of the speech organs. How large Sejong's personal share was is assessed differently.

Joseon was a young state that made Neo-Confucianism its state ideology and restricted Buddhist institutions. Towards Ming China, Joseon was a tributary state: it formally recognised the emperor but governed itself. Classical Chinese remained the language of government and scholarship, so reading and writing were largely reserved for the elite.

Along the borders there were conflicts with Jurchen groups in the north and with Japanese pirates along the coasts. Under Sejong new fortresses were built in the north and the border moved up to the Amnok (Yalu) and Duman (Tumen) rivers. In 1443 trade arrangements were agreed with the lord of Tsushima.

The new alphabet met resistance from scholars such as Choe Malli, who feared it would harm Chinese learning and relations with the Ming. In the following centuries it was used mainly in letters, religious texts and popular literature, including by women, while the official script remained Chinese. Only in the late 19th and 20th centuries did Hangul become Korea's general script.

The scientific and agricultural projects strengthened the state's ability to manage harvests, taxes and timekeeping. The fortresses in the north roughly established the present northern border of the Korean peninsula. Under his successors some institutions became entangled in political conflict; King Sejo abolished the Jiphyeonjeon in 1456.

In his last years Sejong suffered from illnesses, probably including diabetes, and left more and more affairs to Crown Prince Munjong. He died in 1450 in Hanseong. His tomb, Yeongneung, was moved to Yeoju in 1469 and belongs to the Royal Tombs of the Joseon Dynasty, a World Heritage Site since 2009.

In South Korea 9 October is Hangul Day and Sejong appears on the 10,000-won banknote; North Korea celebrates the alphabet's day on 15 January. In Korea Sejong is called 'the Great' and regarded as a model ruler. Historians point out that this image was partly shaped by later national historiography and that his reforms were the work of a broad court.