Traidenis (died 1282) was Grand Duke of Lithuania from 1269 or 1270 until 1282. He is the second most prominent grand duke of Lithuania in the 13th century after Mindaugas. His reign ended a seven-year unrest period after King Mindaugas was assassinated in 1263 and firmly established Lithuania as a pagan state for another hundred years.
Traidenis expanded the Grand Duchy into the territories of Sudovians and Semigalians and strengthened its presence in Black Ruthenia. Unlike Mindaugas, Traidenis did not concentrate on expansion into the east.
Rise to power
While his ancestry is unknown, it is known that he came from Aukštaitija, and before becoming the Grand Duke, he was Duke of Kernavė. On the eve of Traidenis' ascension to the throne in 1268, the legitimacy of the Lithuanian monarch as an institution was compromised. In 1264, Vaišelga Mindaugaitis, who had temporarily renounced his Orthodox monk's vows, ascended to the Lithuanian throne of his murdered father, King Mindaugas, and consolidated his power in the country. He relied consistently on the military forces of the princes of Halych-Volhynia. Consequently, he was compelled to share the authority in Lithuania with them, appointing Vasylko Romanovych, the Prince of Volhynia, as the supreme ruler (sovereign) of Lithuania and bestowing his brother-in-law, Shvarn, the Prince of Halych, with control over Navahrudak and its dependent domains. Nevertheless, effective power within the state remained vested in Grand Duke Vaišelga.
Traidenis, known for his devotion to Lithuanian polytheism and anti-German attitude, was also successful in fighting against the Livonian Order. In 1270, he won the Battle of Karuse, fought on ice near Saaremaa, and killed Otto von Lutterberg, master of the Order. A new master, Andreas von Westfalen, sought quick revenge, but was also killed by Traidenis. However, by 1272 the Order retaliated, attacking Semigalia and building Dinaburg Castle in 1273 on lands nominally controlled by Traidenis. Despite four siege engines used to throw boulders, he was unable to capture the new fortress and had to retreat in 1278. In 1279, the order attacked Lithuanian lands, reaching as far as Kernavė, but on their way back, they suffered a great defeat in the Battle of Aizkraukle. The Order's master, Ernst von Rassburg, became the third master to be killed by Traidenis. The defeat encouraged the conquered Semigallians to rebel against the Order. The Semigallians, led by Nameisis, were now willing to acknowledge Lithuania's superiority and asked Traidenis for assistance. Traidenis supported the revolt, ultimately incorporating segments of their lands into Lithuania. Though unable to provide timely support for the faltering Great Prussian Uprising, Traidenis launched military campaigns to aid the Yotvingians and Sudovians against Teutonic Order conquests, subsequently annexing portions of their territories to the Grand Duchy of Lithuania. He granted asylum to Prussian and Skalvian refugees fleeing to Lithuania. Traidenis is the first known Lithuanian monarch to have died a natural death. All others before him were assassinated or killed in battle.
Family
;Brothers
- Bardis, Liesis, and Svalkenis were Eastern Orthodox and died in fights with Galicia–Volhynia
- Sirputis assisted his brother in military campaigns
;Daughter
- Gaudemunda, married Bolesław II, Duke of Masovia, becoming Duchess of Masovia