As a young boy, Herkus was taken hostage by the Teutonic Knights and brought to Magdeburg, Germany. Having lived there for about ten years, and having studied at the monastery school of St. Johannes der Täufer auf dem Berge, Herkus became well-educated. He was probably baptised as "Henricus", but after his release he dropped two letters from his name and called himself "Hercus" or "Herkus". Since he was familiar with German military tactics, the Natangians elected him as a leader of their forces. At first he was successful: on 21 January 1261 he defeated the Knights in the Battle of Pokarwis. In 1262, he was severely wounded during a Siege of Königsberg. However, he soon recovered, and the following year he invaded the Chełmno Land with a large force. On his way back to Natangia, Herkus and his men were confronted by a contingent of their enemies; in the ensuing Battle of Löbau, a Master and a Marshal, together with 40 knights and a number of other soldiers, were killed.