The Korean king Sejo (1417-1468) was an effective yet cruel ruler. In his attempt to maintain royal prerogative against the pressures of the Confucianist gentry-officials, his ruthlessness nurtured a reaction which in time led to a net loss of power for his successors.

Sejo, formally named Yi Yu, and known as Prince Suyang before taking the throne, was born Nov. 7, 1417, the second son of the great king Sejong. Among eight royal heirs Sejo was perhaps the most capable, but since the designation as crown prince had gone to his elder brother (Yi Hyang, who reigned as Munjong, 1450-1452), Sejo was from the beginning cut off from the succession. Throughout Sejong's reign the royal brothers worked well together, directed by an even-handed father who kept them busy. Sejo was well informed on military affairs, having observed frontier operations against the Jürchen and participated in the development of...