Task: Question Generation
Input (English): Passage: There is considerable uncertainty about the identities of the Grand Dukes of Lithuania between Traidenis' death in 1282 and Vytenis' assumption of power in 1295. This is in part because the two main sources for Lithuanian history in the 13th century, the Hypatian Codex and the Livonian Rhymed Chronicle, end in the early 1290s. In 1285, one chronicle mentions Daumantas as Grand Duke. He attacked the Bishop of Tver and was severely wounded or even killed in the battle. However, that is the only information about him.
The Gediminid dynasty began its ascent in Lithuania during this time with the emergence of its first leader, Butigeidis. In 1289, leading about 8,000 troops, he attacked Sambia. In 1289 the Teutonic Knights built a castle in present-day Sovetsk (Tilsit) and their raids intensified. Butigeidis was the first to build strong castles along the Neman River. He died in 1290 or 1292, and his brother Butvydas (also known as Pukuveras) inherited the crown. Butvydas was the father of Vytenis and probably of Gediminas. During his short reign Butvydas tried to defend the duchy against the Teutonic Knights; he also attacked Masovia, an ally of the knights. His son, Vytenis, advanced to power in 1295 and ended the period of relative instability. His reign marks the transition from the state's establishment to the point at which it was poised for expansion.
Output (English): What did Butiegeidis attack?