The Battle of Svolder (Svold or Swold) was a large naval battle during the Viking age, fought in September 1000 in the western Baltic Sea between King Olaf of Norway and an alliance of the Kings of Denmark and Sweden and Olaf's enemies in Norway. The backdrop of the battle was the unification of Norway into a single independent state after longstanding Danish efforts to control the country, combined with the spread of Christianity in Scandinavia.
King Olaf Tryggvason was sailing to, or home from, an expedition in Wendland (Pomerania), when he was ambushed by an alliance of Svein Forkbeard, King of Denmark, Olof Skötkonung (also known as Olaf Eiríksson or Olaf the Swede), King of Sweden, and Eirik Hákonarson, Jarl of Lade. According to the Saga of King Olaf I Tryggvason, he had 60 warships plus the contribution of 11 warships from the Jomvikings. His ships were captured one by one, last of all the Ormen Lange, which Jarl Eirik captured as Olaf threw himself into the sea. After the battle, Norway was ruled by the Jarls of Lade allied (as a suzerain) to both the Danish Crown and the Commonwealth of Uppsala, Sweden.