Task: Question Generation
Input (English): Passage: As promised, Mindaugas and his wife Morta were crowned at some time during the summer of 1253, and the Kingdom of Lithuania, proclaimed by the pope in 1251, was soundly established. 6 July is now celebrated as "Statehood Day" (Lithuanian: Valstybės diena); it is an official holiday in modern Lithuania. However, the exact date of the coronation is not known; the scholarship of historian Edvardas Gudavičius, who promulgated this date, is sometimes challenged. The location of the coronation also remains unknown.
The Livonian Order used this period to consolidate their control over Samogitian lands. They built three castles along the border: Memelburg (Klaipėda), Georgenburg (Jurbarkas), and Doben (Durbe in Latvia). The Samogitians responded by electing Algminas as their war leader, and attacked Courland, as the Order had limited battlefield successes. In 1259, the Livonian Order lost the Battle of Skuodas, and in 1260, it lost the Battle of Durbe. The first loss encouraged a rebellion by the Semigalians, and the later loss spurred the Prussians into an uprising against the Order. The Great Prussian Uprising lasted for 14 years. Encouraged by Treniota, his nephew, Mindaugas broke peace with the Order. Some chronicles hint that he also returned to his former pagan beliefs, but this is disputable. Nevertheless, all the diplomatic achievements made since his coronation were lost.Mindaugas then formed an alliance with Alexander Nevsky of Novgorod and marched against the Order. Treniota led an army to Cēsis and battled Masovia, hoping to encourage all the conquered Baltic tribes to rise up against the Orders and unite under Lithuanian leadership. He waged successful battles, but did not manage to capture the fortified castles or spark a coalition of Baltic forces against the Order. His personal influence grew because Mindaugas was concentrating on the conquest of Russian lands, dispatching a large army to Bryansk. Treniota and Mindaugas began to pursue different priorities. In the midst of these events, Mindaugas' wife Morta died, and Mindaugas expressed the wish to marry Daumantas' wife. Daumantas and Treniota responded to this insult by assassinating Mindaugas and two of his sons, Ruklys and Rupeikis, in 1263. Lithuania lapsed into years of internal instability.
Output (English): What is thename of the person that fought successful battles but did not manage to spark a coalition of Baltic forces against the Order?