Harthacnut was born in 1018. Harthacnut is Knud's little son. After Knud was killed, the Danish people did not swear to Harold. And Harold was not interested in Denmark because of problems in England. Harthacnut then went to Denmark in 1035 and proclaimed himself a Danish king.
Harthacnut finished the rebellions in Denmark. And all the Danish people supported Harthacnut as king. In 1040, Harold died. Harthacnut, who then went to England, proclaimed himself king of England.
But England has formed a solid army. And the confidence of the British army came to life because of the victories over Harold. Harthacnut tried to reinforce the Viking army, but failed. And England army conquered the all Harthacnut places.
Harthacnut died in 1042.