Chronicles and historical documents of the 13th through 16th centuries contain the first sources about songs relating the heroics of those fallen in battle against the Teutonic Knights. Later songs mention the Swedes, there are frequent references to Riga and Battle of Kircholm; songs collected in the early 19th century mention battles with the Tatars. Songs from uprisings and revolutions, as well as anti-Soviet guerrilla resistance in 1945-1952 and deportation songs are also classified as wartime historical songs.