Casimir III the Great
Succession

In 1355, in Buda, Casimir designated his nephew Louis I of Hungary as his successor should he produce no male heir, just as his father had with Charles I of Hungary to gain help against Bohemia. In exchange Casimir gained a favourable Hungarian attitude, needed in disputes with the hostile Teutonic Order and the Kingdom of Bohemia. At the time Casimir was 45 years old, and so producing a son did not seem unreasonable.

Casimir left no legal son, however, begetting five daughters instead. He tried to adopt his grandson, Casimir IV, Duke of Pomerania, in his last will. The child had been born to his eldest daughter, Elisabeth, Duchess of Pomerania, in 1351. This part of the testament was invalidated by Louis I of Hungary, however, who had traveled to Kraków quickly after Casimir died (in 1370) and bribed the nobles with future privileges. Casimir III also had a son-in-law, Louis VI of Bavaria, Margrave and Prince-elector of Brandenburg, who was considered a possible successor, but he was deemed ineligible as his wife, Casimir's daughter Cunigunde, had died in 1357 without issue.

Thus King Louis I of Hungary became successor in Poland. Louis was proclaimed king upon Casimir's death in 1370, though Casimir's sister Elisabeth (Louis's mother) held much of the real power until her death in 1380.
detectable_format:number_bullet_lists[6]