Livonian Brothers of the Sword
Livonian Brothers of the Sword, aka Christ Knights was a knightly order started in 1202 by Albert von Buxhövden, bishop of Riga and composed of German "warrior monks". It was primarly based on the rules of Templars.
Since the founding the order tended to cancel its dependency to the bishops. In 1218 the bishop asked for help the Danish king, Valdemar II - but he instead made an agreement with the Sword Brothers order and conquered the north of Estonia.
The Lithuanians beat the Brothers at the battle of Siauliai in 1236. Next year the order joined with Teutonic Knights from Prussia, switching to their rules but maintaining administration independence in their conquered lands. Between 1288–1290 they managed to conquer all of Courland, Livonia. In 1346 the united orders bought rest of Estonia from Valdemar IV Atterdag, king of Denmark.
In the mid of XV century with the decline of Teutonic Order, the Sword Borthers decided to reinvent their independece. In 1557 Polish king Sigimund II Augustus intervenied into a war between the bishop of Riga and the Brothers. After an agreement with the king, the last grandmaster of the order, Gotthard Kettler secularized the order, and converted to Lutheran church. In the south part of the Brothers' lands he created a principality of Courland and Semigalia. After the nothern war most of the other lands was ceased to Poland and Lithuania. The north of Estonia was taken back by Denmark.