Well, the phenomena you asked in OP certainly occurred in the late 13th and early 14th century Denmark (especially latter, ca, 1290-1340).
Unfortunately, though, I cannot recommend any valuable study resource for this period, one of the ‘darkest’ one in Danish medieval historiography especially for non-Danish speakers, in English (Cf. Sawyer & Sawyer 1993: 69f.; Skovgaard-Petersen 2003; 366; Bagge 2014: 242-44). While the works of Sawyers and Bagge are accessible one, they sketch an outline of ‘Scandinavian’ history and not so easy to follow the track of political development of high medieval Denmark.
Possible alternative is to google-translate the following URL site from Danish into English, especially the three subsections, ‘Valdemarstiden 1157-1241 (The Valdemar Era, 1157-1241)’, ‘Indre og ydre magtkampe 1241-ca. 1300 (Power Struggles both inside and outside, 1241-ca. 1300)’, and ‘Kongemagtens opløsning ca. 1300-1340 (the Dissolution of Royal Power, ca. 1300-1340)’:
https://danmarkshistorien.dk/perioder/hoejmiddelalderen-ca-1050-1340/
This site is organized by the Department of History and Classic, Aarhus University in Denmark, and the author, Anders Bøgh, is one of very few specialists in this field (high medieval and later medieval Denmark).
I’ll also just make a very brief sketch of how the royal financial crisis occurred in 13th and 14th century Denmark.
#01: Setback of Medieval Denmark as its ‘Baltic Dominion’ in the Middle of the 13th Century
Geopolitically, Denmark is located in the crossroad between South (Continental Europe) and North (Scandinavia), and between West (North Sea) and East (Baltic Sea) as well, and has only very flat landscape (the highest ‘mountain’ in Denmark is just below ca. 180 meter high). In other words, Denmark has very good access from almost all directions, not only for the Danes themselves, but also for their enemies (It may be good to remind how Nazi Germany succeeded in their invasion in Denmark in 1940). The historical development of Denmark during Valdemar Period (1157-1241) show this strength as well as weakness of the Denmark from geopolitical point of view.
At the wake of what we call ‘German Eastern Settlement (Ostsiedlung)’ in the High Middle Ages, it was in fact the Danes that expanded their hegemony first to the southern coast of the Baltic, then also to the Eastern Baltic like Estonia, as shown in this map (Danish Hegemony around the Baltic in 1219). The military alliance between the Valdemar rulers (Valdemar I the Great (d. 1185) and his two sons, namely Cnut VI (d. 1202) and Valdemar II Sejr (the Victorious, d. 1241)) and the Hvides, very powerful magnate family in Sjælland, Denmark enabled this expansionist policy of 12th and 13th century Denmark. The most known of all the Hvides is Archbishop Absalon of Lund (now in Sweden), founder of Copenhagen (now capital of Denmark). The Hvide family also got the office of archbishop at that time, and kingdom of Denmark generally enjoyed a close relationship to the Roman Papacy, mediated by the Hvide archbishop such as Absalon. Popes also approved this Danish expansion as a kind of ‘crusading’.
In 1223, sudden this tide changed: King Valdemar II and his son on hunt were ambushed and kidnapped by one of his German vassals, Count Henry the Black of Schwerin and took custody in ca. 3 years. King Valdemar was finally released, but on condition of paying massive amount of ransom, i.e. 45,000 silver mark and took his other sons in hostage. Already during his custody, lesser German aristocrats in Northern Germany who had formerly under his overlordship openly opposed the rule of the Danes and defeats them (that’s why the Danes had to agree to pay such a massive amount of ransom), and the army led by King Valdemar II himself also suffered from the severe defeat again in the battle of Bornhøved in 1227. This financial burden itself as well as severe military setbacks did not immediately turn Denmark into bankruptcy (Valdemar was in fact released when only 18,000/ 45,000 silver mark had been paid), the territorial expansion of the Danes were stopped and the king of the Danes no longer suppressed the growing power of German aristocrats as well as now emerging cities like famous Lübeck, later leader of ‘Hanseatic League’.
#02: Post-Valdemar Period: Divided Kingdoms, Enemies Everywhere
After the death of King Valdemar II, his sons (and their descendant as well), who the king had enfeoffed across the kingdom, began to strive each other after the throne. A series of archbishops like Jakob Erlandsen (r. 1254-1274) and his nephew Jens Grand (d. 1327) also often openly opposed the ruling king. The close alliance between the king and the archbishop/ the Hvide family, that is to say, the presupposition of the strength of Danish monarchy during the Valdemar Eda, had been lost and never came back. The Danish royal family was also drawn further into nexus of complicated inner-Scandinavian politic by dynastic marriage (that would finally lead to the formation of the Kalmar Union in the end of the 14th century). To give an example, the alleged murderers of King Erik Klipping in 1286 who was said ‘to be killed by those who loved him most with 56 stabs’ (Annals of Ryd), including the member of the Hvide family, sought asylum in Norway, and king of Norway who also had a Danish royal blood from his mother side took shelter them in the border castle of SE Norway. On the other hand, Northern German aristocrats and cities now became virtually independent of Denmark and began to build their territorial lordship. In short, kings or throne claimants of Denmark in ca. 1300 had enemies on almost all sides, but they no longer relied on their military power-base like conscripted farmers or the aristocratic cavalry due to the division of power within kingdom.
Kings of Denmark like Erik Menved (d. 1319) and his younger brother Christopher II (d. 1332) had instead increasingly relied heavily on hired mercenaries to deploy the prolonged military operation. Especially Erik Menved did not completely give up the dream of re-building the former Danish Baltic dominion and often intervened Northern German as well as Swedish politics, and it costed very highly, While Christopher opposed his brother’s intervening policy, he also needed money for military as well as dowry purpose. In the end, when King Christopher II was died in 1332, all of the royal property within the kingdom was taken in mortgage, and Denmark experienced the interregnum (no king) period from 1332 and 1340. The real power of Denmark that period was in the hand of German creditors, such as Count Gerhard of Holstein (d. 1340). It was Christopher’s son, Valdemar IV called Atterdag ‘A New Dawn’ (r. 1340-1375) that gave up the Eastern and Southern Baltic completely (he sold Estonia to the Teutonic Order to raise some money) and instead concentrated on re-building the royal finance as well as the recovery of the old Danish dominion only in the Western Baltic, but even he suffered from the severe setback against another rising power of Denmark’s former subject in the Baltic, German city Lübeck and her allied cities in the 1360s. This victory over their old lord indeed paved the way to the so-called Golden Age of the Hanseatic League, so this desparate struggle of the 14th century Danish rulers, such as mortgage, symbolizes the changing hegemony in the Baltic from Denmark to Northern German cities like Lübeck.
Sorry for a very long and clumsy text (especially in my poor English), but I afraid that even this is a oversimplified narrative.
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