The first union between Sweden and Norway had occurred in 1319 when the three-year-old Magnus, son of the Swedish royal Duke Eric and of the Norwegian princess Ingeborg, inherited the throne of Norway from his grandfather Haakon V and in the same year was elected King of Sweden, by the Convention of Oslo.

The boy king's long minority had weakened the royal influence in both countries, and Magnus will lose both his kingdoms before his death.

In Sweden, Magnus’s partialities and necessities had led directly to the rise of a powerful landed aristocracy, and, indirectly, to the growth of popular liberties.

Forced by the incompetence of the magnates to lean upon the middle classes, in 1359 the king summons the first precursor to what will in the next century become the Swedish Riksdag, on which occasion representatives from the towns are invited to appear along with the nobles and clergy.