Jeongjong, 3rd monarch of Goryeo

Jeongjong of Goryeo (923 – 13 April 949) (r. 945–949) was the third monarch of the Goryeo dynasty of Korea. He was the third son of King Taejo, the founder of the kingdom, and was born more than a decade before Goryeo was formally established. His mother was the daughter of a noble from the Chungju region, Yu Geung-dal.
Jeongjong rose to the throne after his half-brother King Hyejong died, and set to reducing the power of various royal in-laws, including Wang Gyu and Pak Sul-hui. However, lacking the support of the Gaegyeong elites, he was unable to substantially strengthen the throne.
In 946, he spent 70,000 sacks of grain from the royal storehouses to support Buddhism in the country. In 947, he had the fortress of Pyongyang constructed as the country's Western Capital. He sought to move the capital from Gaegyeong to Pyongyang, but was not successful.
Jeongjong became paranoid however that people inside the palace were conspiring to kill him and he then started to go insane. After four years of his reign, he died just after he signed a royal decree to make his brother, the fourth prince Wang So (known as Gwangjong), king instead of his son. 