Samogitian uprisings refer to two uprisings by the Samogitians against the Teutonic Knights in 1401–1404 and 1409. Samogitia was granted to the Teutonic Knights by Vytautas the Great, Grand Duke of Lithuania, several times in order to enlist Knights' support for his other military affairs. The local population resisted Teutonic rule and asked Vytautas to protect them. The first uprising was unsuccessful and Vytautas had to reconfirm his previous promises to transfer Samogitia in the Peace of Raciaz. The second uprising provoked the Knights to declare war on Poland. Hostilities escalated and resulted in the Battle of Grunwald (1410), one of the biggest battles of medieval Europe. The Knights were soundly defeated by the joint Polish–Lithuanian forces, but Vytautas and Jogaila, King of Poland, were unable to capitalize on their victory. Conflicts regarding Samogitia, both diplomatic and military, dragged until the Treaty of Melno (1422).