In the first decade of the 13th century the principality of Jersika, also known as Lettia, was allied with the Principality of Polotsk and Lithuanian dukes against the Bishopric of Livonia, but was defeated in 1209.
There were Ortodox churches in Jersika, as by evidence of Livonian Chronicle; many churchlife-related words came into pre-Latvian languages in that time.