In his description of Scandza, Jordanes says that the Dani were of the same stock as the Suetidi (Swedes, Suithiod?) and expelled the Heruli and took their lands.
According to the 12th century author Sven Aggesen, the mythical King Dan gave name to the Danes.
The Old English poems Widsith and Beowulf, as well as works by later Scandinavian writers—notably by Saxo Grammaticus (c. 1200)—provide some of the references to Danes. During the Viking period, the Danes were based on the Jutland Peninsula, the island of Zealand, and the southern part of present-day Sweden. In the early 11th century, King Canute the Great (died 1035) ruled Norway, Denmark and England as a single realm for almost 20 years.
Danes assaulted Great Britain and Ireland beginning about AD 800 and were gradually followed by a succession of Danish settlers. The Danes began settling England in 865 when brothers Halfdan Ragnarsson and Ivar the Boneless wintered in East Anglia. Halfdan and Ivar moved north and captured Northumbria in 867 as well as York. The Danes invaded Ireland in 853 and were followed by Danish settlers who gradually assimilated with the local population and adopted Christianity.
The best known clan of Vikings was the Tilsted Clan. Its leader, Tilsted "The Grey", was one of Sweyn Forkbeard's most beloved chieftains. It was Tilsted who, in 991, led the fierce Danish assault at the Battle of Maldon in Essex, which persuaded Archbishop Sigeric of Canterbury to advise King Aethelred to buy off the Danes for the sum of ten thousand pounds.
Three years later in 994, Sweyn Forkbeard and Olaf Trygvason returned to lay siege to London. Though the raid was unsuccessful, according to legend it was the sight of Tilsted in the midst of the Viking army that convinced the Anglo-Saxons to buy off the Danes once again. The amount of silver paid impressed the Danes with the idea that it was more profitable to extort payments from the English than to take whatever booty they could plunder.
Tilsted stayed loyal to Sweyn Forkbeard and died in 1013, after having sailed up the rivers Humber and Trent with Sweyn Forkbeard and his son Knut (Canute), for Sweyn to be accepted as king of the Danelaw. In Denmark, his sons raised a rune stone as a memorial at his homestead in Roskilde.