In 1639, the cities of Jutland demanded reforms, mainly directed against the nobility and in favor of the peasants. Under the influence of this mood of public opinion, King Christian IV decided to liberate the peasants from serfdom, replace it with cash payments, or simply buy them out. But his attempt failed, as did his proposal to form a standing army. The nobility achieved a special law that prohibited all classes (except the nobility) to petition the king without prior consideration and approval of these petitions by local authorities, that is, the same nobles. Under such circumstances, only external causes could give strength to the opposition.
The intervention of Christian IV in the thirtieth anniversary of the war, which led to a series of defeats and the terrible destruction of the country by the troops of Tilly and Wallenstein, who had owned it all over the world in Lübeck (1629), was the first step in this regard. Both the country and finances were exhausted — and the nobility refused to rectify the difficult situation by sacrificing privileges for this.
The strengthening of Sweden, which in the 17th century sought to play the role of a preeminent power on the Baltic Sea, was a great danger, the more so that both England and Holland, who suffered from an increase in the Sound Dues, were irritated against Denmark.
Almost immediately following the wars with Sweden, supported by Holland, they found in all their brightness the impotence of Denmark. According to the world in Bremsebro (1645) Denmark was forced to free Sweden from the Sound Dues payment, which lowered revenues from 300 thousand to 80 thousand.
After the new war that ended in Roskilde (1658), Denmark lost its possessions in the south and south-west of Scandinavia – Skåne, Blekinge, Halland, the Norwegian regions of Bohuslän and Trondheim, Bornholm Island.
The very existence of the Danish state was again threatened when the Swedish king Charles X Gustav laid siege to Copenhagen in the winter of 1958-59. Only the desperate resistance of the townspeople and the army under the leadership of King Frederick III saved the country from destruction. On May 27 (June 6), 1660, the Copenhagen Peace was concluded , in which Sweden guaranteed Denmark sovereignty, and also returned Denmark to Trondheim and Bornholm.
Denmark lost a significant part of the territory, the right of exclusive ownership of Sound Dues and left the war terribly devastated. A new political situation emerged, in which the old nobility, which actually ruled the state, lost all prestige, leaving Copenhagen to the mercy of fate during the siege. Frederick III, who commanded the defense of the city, became a national hero. The metropolitan burghers, who defended the capital, demanded their participation in government, reforms in the political system of the kingdom, the removal of the aristocracy from the helm of power, access to it by representatives of tax-paying classes, the establishment of hereditary monarchy, and the abolition of tax immunity of the nobility. In this burghers supported the clergy. At the head of the burghers was the capital burgomaster Hans Nansen (1598-1667). The clergy was led by the Copenhagen Bishop Hans Swann (1606-1668), who came from the middle strata, a professor at the University of Copenhagen, who himself was actively involved in the defense of Copenhagen.
In September 1660 in the capital, the last in the history of Denmark, an assembly of estates was opened, which brought together representatives of the nobility, clergy and burghers. Reluctantly agreeing to a new tax, the nobles fiercely resisted changing the state system. When the State Council rejected the estates ’proposal to introduce hereditary rule, the king and the coalition of the burghers and clergy decided to use force. The mercenary royal army and the burgher police locked the city gates, preventing the nobles from leaving the city. Having submitted to such strong pressure, the Council, on October 13, 1648, accepts the abolition of the royal oath of the nobility upon the accession to the throne. The power of the monarch was proclaimed hereditary, including through the female line. The right to vote for the king was abolished, and the surrender was abolished: the monarchy proclaimed hereditary, and the rights and privileges of the nobility were abolished. According to the plan of the bourgeoisie, Denmark was to become a hereditary estate-constitutional monarchy. Both the Diet of representatives of the three estates, and the Council were to be saved with the accession only to the last of 4 deputies from the bourgeoisie and 2 from the clergy from each area of the state. Moreover, it was supposed to destroy serfdom . Confidence that it would be so, was so great that Copenhagen was overrun by peasants, who submitted a special petition to the king demanding reforms.
Sources:
Denmark // Encyclopedic Dictionary of Brockhaus and Efron
Helge Paludan, Eric Ulsig, Carsten Rasmussen, Hertz Boncerup, Eric Petersen, Henning Poulsen, Søren Rasmussen. History of Denmark