King Sejong the Great ~ Sejong the Great (May 15, 1397 – April 8, 1450, r. 1418–1450) was the fourth king of theJoseon Dynasty of Korea. During his reign, he reinforced Korean Confucian policies and executed major legal amendments. He also used the creation of Hangul and the advancement of technology to expand his territory. He was the third son of King Taejong and Queen Consort Wonkyeong.
Sejong is one of only two Korean rulers posthumously honored with the appellation "the Great", the other being Gwanggaeto the Great of Goguryeo.
Why I said, King Sejong is the Great is because of His services towards His country on strengthening of Korean Military. King Sejong was an effective military planner. He created various military regulations to strengthen the safety of his kingdom, supported the advancement of Korean military technology, including cannon development. Different kinds of mortars and fire arrows were tested as well as the use of gunpowder.
In May 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 to remove the nuisance of Japanese pirates who had been operating out of Tsushima Island. During the expedition, 243 Japanese were killed, and another 110 were captured in combat, while 180 Korean soldiers were killed. 146 Chinese and 8 Korean kidnapped were liberated by this expedition. In September 1419 the Daimyos of Tsushima and 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 with preferential rights regarding trade between Japan and Korea.