Greater Poland Civil War

The Greater Poland Civil War (Polish: Wojna domowa w Wielkopolsce) refers to the conflict that took place during 1382–1385 in the Greater Poland province of the Kingdom of Poland during the interregnum period following the transition of power between the Piast dynasty, Angevin dynasty and the Jagiellon dynasty.

Another name for the conflict is the Grzymała-Nałęcz Family War (Polish: Wojna Grzymalitów z Nałęczami), as a major part of the conflict involved the struggle between the Grzymała and Nałęcz families (clans) for the dominant position in the Greater Poland.

The death of Casimir III the Great in 1370 marked the end of the Piast dynasty in Poland. He was succeeded by Louis I of Hungary of the Angevin dynasty, who was Casimir's nephew. Louis' death in 1382, without a male heir, left a power vacuum (interregnum). Although the Privilege of Koszyce stipulated that one of his daughters would succeed him on the Polish throne, Louis' selection of his daughter Mary proved controversial, as her husband, Sigismund of Luxembourg, was not popular in Poland. The different factions in Poland could not agree on the succession, and a conflict erupted. The faction gathered around the Grzymała clan supported Sigismund, while the Nałęcz clan instead favored the Duke of Masovia, Siemowit IV.

...
Wikipedia