Sejong the Great of Joseon

Sejong the Great (May 6, 1397  – May 18, 1450, r. 1418 - 1450) was the fourth king of the Joseon Dynasty of Korea. He is best remembered for creating the Korean alphabet hangul, despite strong opposition from the scholars educated in hanja (Chinese script). Sejong is one of only two Korean rulers posthumously honored with the appellation "the Great," the other being Gwanggaeto the Great of Goguryeo.

Early life

Sejong was the third son of King Taejong. When he was twelve, he became Grand Prince Chungnyeong' (충녕대군; 忠寧大君) and married a daughter of Shim On (심온; 沈溫) of Cheongsong (청송; 靑松), commonly known as Lady Shim (심씨; 沈氏), who later was given the title Queen Consort Soheon (소헌왕후; 昭憲王后).

As a young prince, Sejong excelled in various studies and was favored by King Taejong over his two older brothers.

Sejong's ascension to the throne was different from those of most other kings. The eldest prince, Yangnyeong (양녕대군), viewing himself as lacking in the requisite skills for kingship, believed that Sejong was destined to become king. Together with the second Prince Hyoryeong (효령대군), he believed it was their duty to place Sejong as king. So they acted extremely rudely in the court, and soon were banished from Seoul. This plot of the two princes ultimately brought Sejong to the throne. The eldest prince became a wandering traveler and lived in the mountains. The second son traveled to a Buddhist temple, where he became a monk.

In August of 1418, following Taejong's abdication two months earlier, Sejong ascended the throne. However, Taejong still retained certain powers at court particularly regarding military matters until he died in 1422.

Strengthening of Korean Military

King Sejong was an effective military planner. In May of 1419, King Sejong, under the advice and guidance of his father Taejong, embarked upon the Gihae Eastern Expedition, the ultimate goal of this military expedition was to remove the nuisance of Japanese pirates who had been operating out of Tsushima. During the expedition, 243 Japanese were killed, and another 110 were captured in combat, while 4 Korean soldiers were killed. At least 140 kidnapped Chinese were liberated by this expedition. In September of 1419 the Daimyo of Tsushima, Sadamori, capitulated to the Joseon court.

The Treaty of Gyehae was signed in 1443, in which the Daimyo of Tsushima recognized and obeyed the suzerainty of the King of Joseon; in return, the Joseon court rewarded the Sō clan preferential rights regarding trade between Japan and Korea.

On the northern border, Sejong established four forts and six posts (hangul: 사군육진 hanja: 四郡六鎭) to safeguard his people from the hostile Chinese and Manchurian nomads living in Manchuria. He also created various military regulations to strengthen the safety of his kingdom. King Sejong supported the advancement of Korean military technology and cannon development increased. Different kinds of mortars and fire arrows were tested as well using gunpowder.

In 1433, Sejong sent Kim Jong-seo (hangul: 김종서, hanja: 金宗瑞), a prominent general, north to destroy the Manchu. Kim's military campaign captured several castles, pushed north, and restored Korean territory, roughly the present-day border between North Korea and China.

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