Above: A penny from Håkon V Magnusson
Magnusson was the youngest son of Magnus Lagabøte
(the Lawmender). Magnus had made Håkon a duke, a title reserved for
men of royal descent. His duchy included the Norwegian mainland provinces
of Østlandet, Agder and Ryfylket as well as the Faeroe Islands and
the Shetlands. As duke, Håkon had full governmental authority. He
established his own administration for the duchy with Oslo
as its capital. When his older brother Eirik died, Håkon was made
king. Being the seat of the king's chancery, Oslo now supplanted Bergen
as the capital city.
Håkon managed to maintain strict control of the English merchants trading in Norway, but had to yield to the Hanseatic tradesmen who were now gaining a foothold in Norwegian cities.
Relations with Denmark being somewhat strained, Håkon fostered closer ties with Sweden. Eventually, Duke Erik, brother of the Swedish king, Birger, was married to Håkon's daughter Ingebjørg. Since she was Håkon's only child from his marriage to Queen Eufemia, Håkon changed the law of succession to extend primogeniture to the first son born by his daughter.
When Håkon Magnusson died in 1319, Ingebjørg's son, Magnus Eriksson was made king in Norway. Two months later he was chosen as king of Sweden. This marked the beginning of the Norway-Sweden Union.