Halfdan the Mild was the son of king Eystein Halfdansson

Eystein Halfdansson

Eystein Halfdansson was the son of Halfdan Hvitbeinn of the House of Yngling according to Heimskringla. He inherited the throne of Romerike. He was known by his nickname Eysteinn Fart, an Old Norse name, possibly meaning "the swift".His wife was Hild, the daughter of the king of Vestfold, Erik...

, of the House of Yngling and he succeeded his father as king, according to Heimskringla

Heimskringla

Heimskringla is the best known of the Old Norse kings' sagas. It was written in Old Norse in Iceland by the poet and historian Snorri Sturluson ca. 1230...

. He was king of Romerike

Romerike

Romerike is a traditional district located north-east of Oslo, in what is today south-eastern Norway. It consists of the Akershus municipalities Fet, Lørenskog, Nittedal, Rælingen, Skedsmo, Sørum and Aurskog-Høland in the southern end , and Ullensaker, Gjerdrum, Nannestad, Nes, Eidsvoll and Hurdal...

 and Vestfold

Vestfold

is a county in Norway, bordering Buskerud and Telemark. The county administration is in Tønsberg.Vestfold is located west of the Oslofjord, as the name indicates. It includes many smaller, but well-known towns in Norway, such as Larvik, Sandefjord, Tønsberg and Horten. The river Numedalslågen runs...

.

He was said to be generous in gold

Gold

Gold is a chemical element with the symbol Au and an atomic number of 79. Gold is a dense, soft, shiny, malleable and ductile metal. Pure gold has a bright yellow color and luster traditionally considered attractive, which it maintains without oxidizing in air or water. Chemically, gold is a...

 but to starve his men with food. He was a great warrior who often pillaged and gathered great booty.

His wife was Liv, the daughter of king Dag of Vestmar. Halfdan the Mild died of illness in his bed.

He was succeeded by his son, Gudrød the Hunter

Gudrød the Hunter

Gudrød the Hunter was a semi-legendary king in Vingulmark in south-east Norway, during the early Viking Age from 804 until 810...

.

According to the historian Halvdan Koht

Halvdan Koht

Halvdan Koht was a Norwegian historian and politician representing the Labour Party.As a politician he served as the Norwegian Minister of Foreign Affairs from 1935 to 1941. He was never elected as a member of the Parliament of Norway, but was a member of Bærum municipal council in 1917–1919 and...

, Halfdan may have been the one to win independence

Independence

Independence is a condition of a nation, country, or state in which its residents and population, or some portion thereof, exercise self-government, and usually sovereignty, over its territory....

 for Vestfold during the turbulent years of 813-14. The Frankish annals state that the kings of Hedeby

Hedeby

Hedeby |heath]]land, and býr = yard, thus "heath yard"), mentioned by Alfred the Great as aet Haethe , in German Haddeby and Haithabu, a modern spelling of the runic Heiðabý was an important trading settlement in the Danish-northern German borderland during the Viking Age...

 had to solve an uprising in Vestfold at this time. According to Ynglingatal

Ynglingatal

Ynglingatal is a skaldic poem listing the kings of the House of Ynglings, dated by most scholars to the late 9th century.The original version is attributed to Þjóðólfr af Hvini who was the skald of a Norwegian petty king named Ragnvald the Mountain-High and who was a cousin of Harald Fairhair...

, Halfdan´s people "gained victory" in this uprising, and Halfdan is thus the first independent ruler of Vestfold.