Battle of Svolder
In the Battle of Svolder in 1000, Eric, Sweyn, and Olof ambushed king Óláfr Tryggvason by the island of Svolder. The place cannot now be identified, as the formation of the Baltic coast has been much modified in the course of subsequent centuries. Svolder was an island probably on the North German coast, near Rügen.
During the summer, King Olaf had been in the eastern Baltic. The allies lay in wait for him at the island of Svolder on his way home. The Norwegian king had with him seventy-one vessels, but part of them belonged to an associate, Jarl Sigvaldi, a chief of the Jomsvikings, who was an agent of his enemies, and who deserted him. Olaf's own ships went past the anchorage of Eric and his allies in a long column without order, as no attack was expected. The king was in the rear of the whole of his best vessels. The allies allowed the bulk of the Norwegian ships to pass, and then stood out to attack Olaf.
Olaf refused to flee, and turned to give battle with the eleven ships immediately about him. The disposition adopted was one which is found recurring in many sea-fights of the Middle Ages where a fleet had to fight on the defensive. Olaf lashed his ships side to side, his own, the Long Serpent, the finest war-vessel as yet built in the north, being in the middle of the line, where her bows projected beyond the others. The advantage of this arrangement was that it left all hands free to fight, a barrier could be formed with the oars and yards, and the enemy's chance of making use of his superior numbers to attack on both sides would be, as far as possible, limited — a great point when all fighting was with the sword, or with such feeble missile weapons as bows and javelins. Olaf, in fact, turned his eleven ships into a floating fort.
Norse writers, who are the main authorities, gave all the credit to the Norwegians, and according to them all the intelligence of Olaf's enemies, and most of their valour, were to be found in Eric. They say that the Danes and Swedes rushed at the front of Olaf's line without success. Eric attacked the flank. His vessel, the Iron Ram (ON Járnbarðinn), was "bearded", that is to say, strengthened across the bows by bands of iron, and he forced her between the last but one of Olaf's line. In this way the Norwegian ships were carried one by one, till the Long Serpent alone was left. At last she too was overpowered. Olaf leapt into the sea holding his shield edgeways, so that he sank at once and the weight of his hauberk dragged him down. Eric captured Olaf's ship, the Long Serpent, and steered it from the battle, an event dwelled upon by his court poet Halldórr ókristni.