Early life He was the second son of
Goryeo General Yi Song-gye and his second wife, Queen Sindeok, and the younger brother of Prince Muan. Yi Song-gye had two wives, both of whom were his legal wives. In July 1392, Yi Song-gye founded the
Joseon Dynasty and became its first king.
Crown prince He was elected crown prince on 7 September 1392 in the first year of King Taejo's reign. In this way, he overcame his older brothers. Later, Yi Pangwŏn and others claimed that
Chŏng Tojŏn and his supporters chose him as crown prince. No evidence confirms that Yi Pangsŏk was elected crown prince by Chŏng Tojŏn. During his reign as crown prince, his wife Hyeonbin Ryu and
eunuch Yi Man (이만, 李萬) committed adultery, which resulted in punishment for both. Hyeonbin Ryu was deposed and banished from the palace whereas Yi Man was beheaded in 1393. Hyeonbin Shim was chosen as the crown prince's new wife in 1397. On 15 September 1396, the crown prince's mother, Queen Sindeok, died.
First Strife of Princes On 6 October 1398, the First Strife of Princes began under the leadership of
Prince Jeongan Yi Bang Won. The crown prince personally led the army against Prince Jeongan's forces stationed in front of
Gwanghwamun Gate, but he refused to confront the rebels after officer Bong Won-ryang (봉원량, 奉元良) reported, “From Gwanghwamun to Namsan, the elite cavalry is fully equipped". After killing enemies such as Chŏng Tojŏn, Nam Ŭn (남은, 南誾; 1382–1398), Shim Hyosaeng (심효생, 沈孝生; 1348–1398), and Park Wi (박위, 朴葳; ?-1398), Prince Jeongan chose Yi Panggwa, Prince Yeongan, his older brother, as crown prince. The deposed Crown Prince Yi Bang Seok, who was to be exiled, was later sent from
Gyeongbokgung Palace through the Yeongchumun Gate. With the approval of the Dopyeonguisasa assembly, Prince Jeongan's supporters, including Yi Geo-yi (이거이, 李居易; 1348–1412), commissioned assassins to assassinate the deposed crown prince. He was then known as Deposed Crown Prince Yi Bang-seok (폐세자 이방석, 廢世子 李芳碩), but was posthumously just titled as Sodo (소도, 昭悼). == After death ==