Erik learned of his father's death as he was on the point of embarking for England to press his suit for the hand of Queen Elizabeth I. Back in Stockholm he summoned a
Riksdag, which met at
Arboga on 15 April 1561. There he adopted the royal propositions known as the "Arboga articles", considerably curtailing the authority of the royal dukes, his half-brothers John and
Charles, in their respective provinces. He was crowned as Erik XIV, but was not necessarily the 14th king of Sweden named Erik. He and his brother Charles adopted regnal numbers according to
Johannes Magnus's partly fictitious
history of Sweden. There had, however, been at least six earlier Swedish kings with the name of Erik, as well as pretenders about whom very little is known. From the start of his reign, Erik was in opposition to the
Swedish nobility. He chose as a close adviser
Jöran Persson (1530–68), who had narrowly escaped execution under Erik's father. Persson was also opposed to the nobility and a determined opponent of Erik's half-brother, later John III of Sweden (1537–92). John was the
Duke of Finland and was married to a Polish princess, against Erik's wishes, which made him friendly with Poland. John pursued an expansionist policy in Livonia (now Estonia and Latvia), in breach of the Arboga articles, which led to contention between the brothers. In 1563, John was seized by an army sent to Finland, and tried for
high treason by Erik's order. Unlike his father, who had been satisfied with ruling an independent state, Erik tried to expand his influence in the
Baltic region and in
Estonia, beginning the process that resulted in Sweden becoming a great power in the 17th century. This expansionism resulted in a clash with his cousin,
Frederick II of Denmark-Norway (1534–88). Most of Erik XIV's reign was then dominated by the
Livonian War and the
Scandinavian Seven Years' War against
Denmark-Norway (1563–70), during which he successfully repelled most Danish-Norwegian attempts at conquest, but was unable to keep his own acquisitions. From 1563 onwards, his insanity became pronounced; his rule became even more arbitrary and marked by violence. His suspicion of the nobility led him to suspicions of the
Sture family, then headed by
Svante Stensson Sture, the brother-in-law of Erik's father. King Erik first acted against the family in 1566, accusing Svante's son
Nils of treason, but commuted the sentence and instead sent Nils to
Lorraine, supposedly to arrange a marriage with Princess
Renata of Lorraine. However, Erik had determined to marry his mistress
Karin Månsdotter and in 1567, on Nils's return and suspicious of high treason, he killed several members of the family in the so-called
Sture Murders, Erik himself stabbing
Nils Svantesson Sture. The king probably thought of the killing as an execution rather than murder. ==Downfall==