The Treaty of 944 between Kievan prince Igor and the Byzantine Empire has the names of many Rus' ambassadors - one of which was Jatviag Gunarev. It is also the first written documentation of the term Jatviag, or Yatviag.
Netimeras, a ruler of the Yotvingians (part of Lithuanian kingdom), was converted to Christianity by Bruno of Querfurt in 1009.
When his father died in 1170, Roman the Great was bequeathed the Principality of Vladimir-in-Volhynia.[1] He subdued the Yotvingians, and harnessed the captives instead of oxen to drag the plows on his estates.[2]
In 1264, the Duke of Krakow, Boleslaw V the Chaste organized an expedition against Yotvingia. On 23 June 1264 the two armies met near Brańsk. The Battle of Brańsk lasted two days pitting the forces of Yotvingia, led by Kumata against the well equipped Krakovian army. The Yotvingian forces were routed in a bloody battle and their leader killed.
In the 1280s the Northern Yotvingians were partly conquered and dispersed by the Teutonic Knights; some Yotvingians then took refuge in the Duchy of Lithuania.