Mindaugas, the duke of southern Lithuania, was among the five senior dukes mentioned in the treaty with Galicia–Volhynia. The Livonian Rhymed Chronicle, reports that by the mid-1230s, Mindaugas had acquired supreme power in the whole of Lithuania. In 1236, the Samogitians, led by Vykintas, defeated the Livonian Order in the Battle of Saule. The Order was forced to become a branch of the Teutonic Knights in Prussia, making Samogitia, a strip of land that separated Livonia from Prussia, the main target of both orders. The battle provided a break in the wars with the Knights, and Lithuania exploited this situation, arranging attacks towards the Ruthenian provinces and annexing Navahrudak and Hrodna.