The Battle of Saule, fought on 22 September 1236, was a pivotal event in the early history of Lithuania. It marked the first major victory of the Baltic tribes—primarily Samogitians and Semigallians—over the Livonian Brothers of the Sword, a Catholic military order tasked with converting the region to Christianity. The battle resulted in the death of the Livonian Master Volkwin and the near destruction of the order, forcing its remnants to merge with the Teutonic Knights in 1237.
This victory not only halted the Livonian advance into Samogitia but also inspired widespread revolts among other Baltic tribes, including the Curonians and Semigallians, reversing years of Christian conquests along the Daugava River. Strategically, the swampy terrain favored the lightly armed Baltic warriors over the heavily armored knights, contributing to the decisive pagan victory.
The aftermath of Saule reinforced Lithuanian unity and further encouraged tribal consolidation, a process essential for the formation of the Grand Duchy of Lithuania. Leaders like Vykintas emerged during this period, and the battle demonstrated the need for a more organized state to resist further incursions from the Livonian and Teutonic Orders. Today, 22 September is commemorated as Baltic Unity Day by Lithuania and Latvia, celebrating this symbolic moment in their shared history.