King Olav subsequently founded the city of Sarpsborg in Viken during 1016 .
Olaf first declared himself king of Norway in 1015 and established control of the nation in battle , principally the Battle of Nesjar in 1016 .
King Olaf subsequently founded the city of Sarpsborg in Viken during 1016 .
Olaf first declared himself king of Norway in 1015 and established control of the nation in battle , principally the Battle of Nesjar in 1016 .