The Battle of Saule was fought on 22 September 1236, between the Livonian Brothers of the Sword and pagan troops of Samogitians and Semigallians. Between 48 and 60 knights were killed, including the Livonian Master, Volkwin. It was the earliest large-scale defeat suffered by the orders in Baltic lands. The Sword-Brothers, the first Catholic military order established in the Baltic lands, was soundly defeated and its remnants accepted incorporation into the Teutonic Order in 1237. The battle inspired rebellions among the Curonians, Semigallians, Selonians, Oeselians, tribes previously conquered by the Sword-Brothers. Some thirty years' worth of conquests on the left bank of Daugava were lost. To commemorate the battle, in 2000 the Lithuanian and Latvian parliaments declared 22 September to be the Baltic Unity Day.

The Livonian Brothers of the Sword was a Catholic military order established in 1202 during the Livonian Crusade by Albert, the third bishop of Riga. Pope Innocent III sanctioned the establishment in 1204 for the second time. The membership of the crusading order comprised warrior monks, mostly from northern Germany, who fought Baltic and Finnic polytheists in the area of modern-day Estonia, Latvia and Lithuania. Alternative names of the Order include Christ Knights, Swordbrothers, Sword Brethren, Order of the Brothers of the Sword, and The Militia of Christ of Livonia. The seal reads: +MAGISTRI ETFRM MILICIE CRI (Christi) DE LIVONIA.