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King Sejong was crowned for 1418~1450

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Jongmu Lee led 227 soldiers and defeated Tsushima.

In 1419, in the 1st year of King Sejong, Tsushima was subjugated to Gyeongsang-do.

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In 1420, Jiphyeonjeon Hall was established as a policy research institution in order to operate the central government system, and they were given preferential treatment beyond general management.

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Agricultural books written by Jeong Cho and Byeon Hyo-moon under the command of Sejong

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Hwang Jong-gwan, a copper tube used as a standard for determining the sound rate, was designated as the standard.

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Sejong himself created 28 characters, regretting that the people could not easily learn Chinese characters, the characters of the time, and that Korean words and Chinese characters did not communicate with each other, so they could not express what they were trying to say.