According to the laws of medieval Norway before the thirteenth century, the national kingship was the king’s allodial possession and was inherited by his sons at his death. All his sons were legal heirs, those of illegitimate birth as well as those who were born in wedlock. When there was more than one heir, the kingship was held jointly, all the claimants receiving the royal title and permission to maintain each his own household. Usually a part of the realm was assigned to each; but it was the administration, and not the kingdom itself, which was thus divided. It is readily seen that such a system would offer unusual opportunities for pretenders; and at least three times in one hundred years men whose princely rights were at best of a doubtful character mounted the Norwegian throne. It is an interesting fact that two of these, the strenuous Sverre and the wise Hakon IV, must be counted among the strongest, ablest, and most attractive kings in the history of Norway.
Though there had been instances of joint rule before the twelfth century, the history of that unfortunate form of administration properly begins with the death of Magnus Bareleg on an Irish battlefield in 1103. Three illegitimate sons, the oldest being only fourteen years of age, succeeded to the royal title. One of these was the famous Sigurd Jerusalemfarer, who took part in the later stages of the first crusade. About twenty years after King Magnus’ death, a young Irishman, Harold Gilchrist by name, appeared at the Norwegian court and claimed royal rights as a son of the fallen king. King Sigurd forced him to prove his birthright by an appeal to the ordeal, but the Irishman walked unhurt over the hot plowshares. Harold became king in 1130 as joint ruler with Sigurd’s son Magnus, later called “the Blind.”[83] Three of his sons succeeded to the kingship in 1136. During the next century several pretenders appeared and civil war became almost the normal state of the country. Between 1103 and 1217 fifteen princes were honored with the royal title; eleven of these were minors. The period closed with the defeat and death of King Hakon’s father-in-law, the pretender Skule, in 1240.
The strife that followed the accession of Harold Gille and Magnus the Blind is the subject of Björnson’s great historical drama, Sigurd Slembe (English translation by William Morton Payne).