From Scandinavia: A History, by Ewan Butler (New Word City, 2016), Kindle pp. 166-167:
The death of Christian VI in 1746 and the succession of his son as Frederick V was welcomed by most Danes.
Meanwhile, in Sweden, effective government was exercised by Count Arvid Horn, celebrated as one of Charles XII’s most daring generals and, later, as a skillful diplomat. As president of the estate of nobles, Horn decided that war-weary Sweden needed a long period of peace, and he had to choose his allies with some care. In 1727, when Horn began his rule, Europe was divided into two rival camps. England-Hannover and France stood opposed to Austria, Spain, and Russia, and Horn finally linked the fortunes of Sweden with the Anglo-French combination.
For eleven years, Horn pursued a pacifist policy, much to the displeasure of a large number of young noblemen who were eager to follow a more aggressive course, an aspiration in which they were supported by many influential businessmen and burgesses. These aggressively minded young men nicknamed Horn’s party the “Nightcaps” or more usually the “Caps,” in tribute to their sleepy conduct of national affairs, and in consequence came to call themselves the “Hats.”
In the 1730s, the alliance between England and France broke up, and the French ambassador in Stockholm, well supplied with money, began to intrigue with the Hats. By the payment of large bribes, he managed to organize a campaign of ruthless agitation and abuse aimed at Horn’s government. In 1739, Horn was forced to resign and his supporters were expelled from the council. The Hats, generally men of the lesser nobility and the bourgeoisie, took over.
The aim of the Hats was to take revenge on Russia, with French help, and the outbreak of the War of the Austrian Succession in 1741 seemed to give them the opportunity that they sought. Beginning with a tripartite contest for the Austrian inheritance and the invasion of Austria by Frederick the Great of Prussia, it was to draw many European nations into the fray. France, Spain, Bavaria, and Sweden came to Prussia’s support, while Britain and Holland joined beleaguered Austria. Separately, Sweden declared war on Russia. The entire conflict, which was fought in many combinations and in many theaters, including the American colonies (where it was known as King George’s War), lasted until 1748.