Queen Jadwiga of Poland, taking the name Władysław II Jagiełło and becoming King of Poland. This created a personal union between the two countries and a potentially formidable opponent for the Teutonic Knights. The Order initially managed to play Władysław II Jagiełło and his cousin Vytautas against each other, but this strategy failed when Vytautas began to suspect that the Order was planning to annex parts of his territory. The baptism of Jogaila began the official conversion of Lithuania to Christianity. Although the crusading rationale for the Order's state ended when Prussia and Lithuania had become officially Christian, the Order's feuds and wars with Lithuania and Poland continued. The Lizard Union was created in 1397 by Prussian nobles in Chełmno Land to oppose the Order's policy. In 1407, the Teutonic Order reached its greatest territorial extent and included the lands of Prussia, Pomerelia, Samogitia, Courland, Livonia, Estonia, Gotland, Dagö, Ösel, and the Neumark, pawned by Brandenburg in 1402. Decline In 1410, at the Battle of Grunwald a combined Polish–Lithuanian army, led by Władysław II Jagiełło and Vytautas, decisively defeated the Order in the Polish–Lithuanian–Teutonic War. Grand Master Ulrich von Jungingen and most of the Order's higher dignitaries fell on the battlefield (50 out of 60). The Polish–Lithuanian army then began the Siege of Marienburg (Malbork), the capital of the Order, but was unable to take Marienburg owing to the resistance of Heinrich von Plauen. When the First Peace of Thorn was signed in 1411, the Order managed to retain essentially all of its territories, although the Knights' reputation as invincible warriors was irreparably damaged. While Poland and Lithuania were growing in power, that of the Teutonic Knights dwindled through infighting. They were forced to impose high taxes to pay a substantial indemnity but did not give the cities sufficient requested representation in the administration of their state. The authoritarian and reforming Grand Master Heinrich von Plauen was forced from power and replaced by Michael Küchmeister von Sternberg, but the new Grand Master was unable to revive the Order's fortunes. After the Gollub War the Knights lost some small border regions and renounced all claims to Samogitia in the 1422 Treaty of Melno. Austrian and Bavarian knights feuded with those from the Rhineland, who likewise bickered with Low German-speaking Saxons, from whose ranks the Grand Master was usually chosen. The western Prussian lands of the Vistula River Valley and the Brandenburg