Christian III of Denmark (1503-1559, r.1533/4-59) made Lutheranism the official state church of Denmark and sided against the Emperor Charles V during the Fourth Hapsburg-Valois War (1542-44).
Christian was the eldest son of Frederick I, king of Denmark and Norway (d.1533). Christian was raised as a Lutheran, and met Martin Luther. In 1526 he served as statholder of Schleswig and Holstein, and protected the Protestant interests in the state.
In 1533 Frederick died, triggering a succession crisis. The largely Catholic state council declared Frederick's younger son Hans to be king. At the same time Copenhagen, Malmo and the German city of Lübeck combined to try and restore Christian II, a former king of Denmark who was then imprisoned in Sonderborg. Lübeck invaded Holstein, starting the Count's War of 1533-36.
Christian III responded by gaining the support of the nobles and bishops of Jutland, who declared him king at Rye in Jutland in August 1534. He invaded Jutland, Fyn and Zealand and captured Copenhagen in 1536, winning the war.
After coming to power Christian arrested the Catholic bishops. He called the Diet of Copenhagen in October 1536 in which the Lutheran Church was established as the state church, existing church property was taken over by the state and the rights of the noble's council (the Rigsrad) were confirmed.
In 1537 Christian brought his religious advisor Johannes Bugenhagen, a Lutheran reformer and theologian at Wittenberg, Germany, to organise the Lutheran Church of Denmark. New bishops, from non-noble backgrounds were appointed, with the title of superintendents.
In 1542 Christian declared war on the Emperor Charles V, in support of the Protestant princes of the Empire. He closed the Sound to Imperial shipping, excluding merchants from the Netherlands from the valuable Baltic trade. The war ended with the Peace of Speyer of 1544. Christian remained neutral during the War of the Schmalkaldic League (1546-47), in which Charles V defeated an alliance of Protestant states.