One of Denmark's most obscure monarchs; little definite is known about the life and reign of Harald II.
It is known he acted as regent for his father while he campaigned in England against Aethelred II and would succeed upon news of his death in early 1014. His younger brother, or half-brother, Cnut was expelled briefly from England and would re-gather support and allies at his brother's court. It is probable that Harald sent him to seek an alliance with Poland during this time. Indeed Harald probably recognised it would be better for his brother to be actively engaged abroad rather than at home potentially stirring up trouble.
In 1018 Harald died, some sources saying he was murdered. Cnut renounced his claim to Wessex and gathered an invasion force to conquer Denmark. He needn't have worried, Denmark quickly accepted him as ruler. Viken would be a little more troublesome to pacify.