Emperor Toba vs Henry IV of Castile

Toba abdicated but continued to govern as a cloistered emperor, following the Insei system established by his grandfather Shirakawa. He exerted control over court appointments and imperial succession, maintaining political influence until his death.

Toba clashed with Fujiwara no Tadazane, the regent, over control of imperial succession. Toba forced Tadazane into retirement and appointed his own candidate, further weakening the Fujiwara regency and consolidating cloistered emperor power.

After Toba's death, a succession conflict erupted between his sons Emperor Go-Shirakawa and retired Emperor Sutoku. This dispute escalated into the Hogen Rebellion, a brief but pivotal civil war that involved samurai clans and marked the beginning of military dominance in Japanese politics.

Henry IV of Castile signed the Treaty of the Bulls of Guisando, recognizing his half-sister Isabella as his legitimate heir instead of his daughter Joanna. This agreement was intended to resolve the succession dispute, but Henry later repudiated it, leading to renewed conflict.

After Henry IV's death, a civil war erupted between supporters of his daughter Joanna la Beltraneja and those of his half-sister Isabella. The war involved Portuguese and Aragonese intervention and ended with Isabella's victory, securing her throne and leading to the union of Castile and Aragon.

During the War of the Castilian Succession, Henry IV's forces lost control of the Canary Islands to Portuguese-backed rebels. The islands were later recovered by Isabella I, but the conflict highlighted the weakness of Henry's reign and the erosion of royal authority.