In 15th century Joseon, King Sejong felt deep sorrow that his people could not read or write. The Chinese characters used at the time were too difficult for commoners to express their thoughts in writing.
King Sejong lamented, "The language of our country is different from that of China, and does not correspond to Chinese characters. Therefore, among the ignorant people, there have been many who, having something they wish to say, have been unable to express their feelings."
However, creating a new writing system was a very radical attempt at the time. In a China-centered worldview, creating an independent writing system was a great adventure.
Nobles, especially some scholars from the Hall of Worthies (Jiphyeonjeon), strongly opposed this. Choe Manri submitted a memorial stating, "Our country has had its own writing since the founding fathers. If we now create and use a new vernacular script, China will consider us barbaric."
Despite this opposition, King Sejong continued his research in secret. After day and night research with young scholars from the Hall of Worthies, he finally completed Hunminjeongeum in 1443.
After a three-year trial period, on the 10th day of the 9th lunar month in 1446, Hunminjeongeum was officially promulgated. This day is the origin of today's Hangul Day.