One of the most notable Semigallian leaders was duke Viestards (Viesturs). Upon uniting hostile Semigallian clans into a single state in the early 13th century, Viestards formed an alliance with the German crusaders to defeat his enemies on the outside. After the crusaders broke the treaty and invaded his lands, he allied with Lithuanians, resulting in the near annihilation of the Livonian Brothers of the Sword in the Battle of Saule in 1236.