<P> From the early 13th century, two German crusading military orders, the Livonian Brothers of the Sword and the Teutonic Knights, became established at the mouth of the Daugava River and in Chełmno Land respectively . Under the pretense of converting the population to Christianity, they proceeded to conquer much of the area that is now Latvia and Estonia, in addition to parts of Lithuania . In response, a number of small Baltic tribal groups united under the rule of Mindaugas . Mindaugas, originally a kunigas or major chief, one of the five senior dukes listed in the treaty of 1219, is referred to as the ruler of all Lithuania as of 1236 in the Livonian Rhymed Chronicle . </P> <P> In 1236 the pope declared a crusade against the Lithuanians . The Samogitians, led by Vykintas, Mindaugas' rival, soundly defeated the Livonian Brothers and their allies in the Battle of Saule in 1236, which forced the Brothers to merge with the Teutonic Knights in 1237 . But Lithuania was trapped between the two branches of the Order . </P> <P> Around 1240, Mindaugas ruled over all of Aukštaitija . Afterwards, he conquered the Black Ruthenia region (which consisted of Grodno, Brest, Navahrudak and the surrounding territories). Mindaugas was in process of extending his control to other areas, killing rivals or sending relatives and members of rival clans east to Ruthenia so they could conquer and settle there . They did that, but they also rebelled . The Ruthenian duke Daniel of Galicia sensed an occasion to recover Black Ruthenia and in 1249--1250 organized a powerful anti-Mindaugas (and "anti-pagan") coalition that included Mindaugas' rivals, Yotvingians, Samogitians and the Livonian Teutonic Knights . Mindaugas, however, took advantage of the divergent interests in the coalition he faced . </P> <P> In 1250, Mindaugas entered into an agreement with the Teutonic Order; he consented to receive baptism (the act took place in 1251) and relinquish his claim over some lands in western Lithuania, for which he was to receive a royal crown in return . Mindaugas was then able to withstand a military assault from the remaining coalition in 1251, and, supported by the Knights, emerge as a victor to confirm his rule over Lithuania . </P>

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