The "Chronicon terrae Prussiae" stated that Herkus was originally from Natangia, one of the lands of the Old Prussians. The Prussians were the first of the Baltic tribes to be conquered by the Teutonic Knights, who first arrived in Chełmno in 1226 at the request of Konrad I of Masovia, whose own struggle with the Prussians had proved unsuccessful. As part of the Northern Crusades, the Knights proceeded to attack the Prussians with the purported aim of converting them to Christianity.