Following the death of Sigismund II Augustus in 1572, the Polish–Lithuanian Commonwealth, which had recently been unified under the Union of Lublin (1569), entered a critical period of transition. The Union had integrated Lithuania into a shared political system with Poland, though Lithuania retained some autonomy. However, with the extinction of the Jagiellonian dynasty, political uncertainty increased. Lithuania, along with Poland, now faced the complexities of noble democracy, which sought to limit the monarch's power. During the first interregnum, the Commonwealth’s nobles strengthened their influence through the establishment of local confederations (kapturs) to maintain public order and lay the groundwork for a new elective monarchy. These developments were crucial in reshaping Lithuanian governance as power shifted more decisively to the nobility.
Stephen Báthory's election in 1576, amidst this decentralized political environment, marked a significant phase in Lithuanian history. Although the magnates initially supported Maximilian II for the throne, opposition from reformists like Jan Zamoyski led to Báthory’s selection. Báthory’s reign introduced military strength to the Commonwealth, especially in conflicts such as the Livonian War against Muscovy. This war had profound implications for Lithuania, as control over Livonia was essential for securing access to trade routes in the Baltic Sea. His victory and the subsequent Truce of Jam Zapolski (1582) solidified the Commonwealth's northern frontier, ensuring Lithuania's influence over these strategic territories, although it also created further tensions with Russia and Sweden.
Within Lithuania, Báthory's reign also reflected the growing reliance of the monarchy on powerful nobles, a dynamic that was mirrored across the Commonwealth. His close collaboration with Jan Zamoyski, who played a key role in both governance and military campaigns, illustrated how the monarchy depended on influential magnates to maintain stability. However, Báthory's tensions with other noble factions, exemplified by the Zborowski affair, revealed the challenges of balancing royal authority with the interests of the aristocracy. These internal conflicts were not just confined to Poland but also affected Lithuanian politics, as the noble class in both regions sought to maximize their power within the new political framework.
Although Báthory initiated reforms, such as the establishment of Lithuanian Tribunals to shift judicial power from the monarchy to the nobility, these measures only deepened the decentralization of authority. His failure to enforce trade regulations through Gdańsk (Danzig) further weakened the Commonwealth’s economy, impacting Lithuania’s economic interests. Despite these setbacks, Báthory's military reforms, including the creation of the piechota wybraniecka (peasant infantry), marked an important step toward modernizing the Commonwealth's army.
Báthory’s death in 1586 left a mixed legacy for Lithuania. While his military successes temporarily secured strategic territories, the dependence on noble goodwill and internal divisions highlighted the structural weaknesses of the elective monarchy. For Lithuania, the reign of Báthory underscored both the potential and limitations of the Union of Lublin: although it provided opportunities for military and territorial expansion, it also exposed the vulnerabilities of a state governed by noble democracy. These unresolved tensions would continue to shape Lithuania’s political landscape in the years that followed, as the Commonwealth increasingly struggled to maintain its cohesion and influence amidst internal conflicts and external pressures.