Polish-Lithuanian Commonwealth (1540s)

Timeline

1. 1541–1544Vilnius · LithuaniaSigismund I ruled both Poland and Lithuania, maintaining the union through joint sejm consultations and shared foreign policy; in the early 1540s the two coordinated military deployments against Muscovite pressure from the east and Tatar raids from the south, while retaining separate legal and administrative systems.
2. 1544Vilnius · LithuaniaIn 1544, Sigismund II Augustus was elected grand duke by the Lithuanian nobility and began independently directing Lithuanian affairs, ensuring the continuation of the Jagiellon line in both realms and setting an institutional precedent for uniting both crowns under one monarch.
3. 1548–1550Kraków · PolandAfter Sigismund I's death, Augustus smoothly succeeded to the Polish throne, creating a situation where one person held supreme rule over both realms; between 1548 and 1550 the crown promoted coordination mechanisms between the two sejms and a common defense policy, evolving the union from a dynastic personal union toward greater institutionalization.