King Sejong of Korea’s crowning achievement is hangul, the Korean alphabet. In 1443 CE, the king and eight of his advisers started the process of developing an alphabetic system to represent the Korean language sounds and sentence structure accurately. The new writing system quickly spread among segments of the population who previously had not had access to enough education to learn the more complicated Chinese writing system such as women and those of the lower social classes. This episode is also worth noting as the king initially faced a backlash from the scholars. 

Read more in History made Beautiful blog.