A king who feared his own heir built a succession war he lost

In 1592 the Imjin War broke out, and with the court fleeing, the ministers pressed King Seonjo to name an heir. He passed over his eldest son Imhae — disgraced by his misdeeds — and made his second son Gwanghae crown prince. Gwanghae led a separate court through the war, rallied the eight provinces, and won the loyalty of the people.

But that popularity turned his father against him. Rather than confirm the succession, Seonjo seated the rival Imhae beside him when meeting Ming generals, and took a young consort who finally bore a son, Grand Prince Yeongchang — a direct threat to Gwanghae's standing. Ming's court rejected Gwanghae's installation five times over, and even after he acceded in 1608 it refused royal investiture and sent envoys to check on the disgraced first son.

Gwanghae never trusted the throne he had won. He banished and killed Imhae, executed the former premier who had backed Yeongchang, had the young prince removed in 1613, and finally imprisoned the queen mother in 1618. The purges emptied the court of critics, and his later foreign policy — balancing Ming against the Jurchen Later Jin — froze the bureaucracy into deadlock. In 1623 the bloodless Injo Restoration deposed him; he was demoted to a mere prince, exiled, and died on Jeju in 1641, aged 67.